Elicitor peptides having disrupted hypersensitive response box and use thereof

ABSTRACT

Disclosed are peptides that induce an active plant response, but not a hypersensitive response, when applied to plant tissue. These peptides also preferably exhibit improved solubility, stability, resistance to chemical degradation, or a combination of these properties. Use of these peptides or fusion polypeptides, or DNA constructs encoding the same, for modulating plant biochemical signaling, imparting disease resistance to plants, enhancing plant growth, imparting tolerance to biotic stress, imparting tolerance and resistance to abiotic stress, imparting desiccation resistance to cuttings removed from ornamental plants, imparting post-harvest disease or post-harvest desiccation resistance to a fruit or vegetable, or enhancing the longevity of fruit or vegetable ripeness are also disclosed.

This application is a continuation of U.S. patent application Ser. No. 15/244,862, filed Aug. 23, 2016, which is a continuation of U.S. patent application Ser. No. 14/872,347, filed Oct. 1, 2015, and issued as U.S. Pat. No. 10,743,538, which claims the priority benefit of U.S. Provisional Patent Application Ser. No. 62/058,535, filed Oct. 1, 2014, and U.S. Provisional Patent Application Ser. No. 62/186,527, filed Jun. 30, 2015, each of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to novel elicitor peptides having disrupted hypersensitive response boxes and their use for inducing active plant responses including, among others, growth enhancement, disease resistance, pest or insect resistance, and stress resistance.

BACKGROUND OF THE INVENTION

The identification and isolation of harpin proteins came from basic research at Cornell University attempting to understand how plant pathogenic bacteria interact with plants. A first line of defense is the hypersensitive response (HR), a localized plant cell death at the site of infection. Cell death creates a physical barrier to movement of the pathogen and in some plants dead cells can release compounds toxic to the invading pathogen. Research had indicated that pathogenic bacteria were likely to have a single factor that was responsible for triggering the HR. A basic aim of the Cornell research was to identify a specific bacterial protein responsible for eliciting the HR. The target protein was known to be encoded by one of a group of bacteria genes called the Hypersensitive Response and Pathogenicity (hrp) gene cluster. The hrp cluster in the bacterium Erwinia amylovora (Ea), which causes fire blight in pear and apple, was dissected and a single protein was identified that elicited HR in certain plants. This protein was given the name harpin (and, later, harpin_(Ea)) and the corresponding gene designated hrpN. This was the first example of such a protein and gene identified from any bacterial species.

A number of different harpin proteins have since been identified from Erwinia, Pseudomonas, Ralstonia, Xanthomonas, and Pantoea species, among others. Harpin proteins, while diverse at the primary amino acid sequence level, share common biochemical and biophysical characteristics as well as biological functions. Based on their unique properties, the harpin proteins are regarded in the literature as belonging to a single class of proteins.

Subsequent to their identification and isolation, it was thereafter discovered that harpins could elicit disease resistance in plants and increase plant growth. An important early finding was that application of purified harpin protein made a plant resistant to a subsequent pathogen attack, and in locations on the plant well away from the injection site. This meant that harpin proteins can trigger a Systemic Acquired Resistance (SAR), a plant defense mechanism that provides resistance to a variety of viral, bacterial, and fungal pathogens.

In crop protection, there is a continuous need for compositions that improve the health of plants. Healthier plants are desirable since they result in better yields and/or a better quality of the plants or crops. Healthier plants also better resist biotic and abiotic stress. A high resistance against biotic stresses in turn allows the growers to reduce the quantity of pesticides applied and consequently to slow down the development of resistances against the respective pesticides.

Harpin_(αβ) is a fusion protein that is derived from several different harpins. Harpin_(αβ) has been shown to suppress nematode egg production, enhance the growth, quality and yield of a plant, and increase a plant's vigor. Its amino acid and nucleotide sequences are described in detail in U.S. Application Publ. No. 2010/0043095.

To date, harpin and harpin_(αβ) production and their use in agricultural and horticultural applications have been as a powdered solid coated on starch. This limits the use and versatility of the harpin proteins, because liquid suspensions of the powdered harpin proteins in water have an effective useful life of only 48-72 hours before significant degradation and loss of activity occurs. Another problem with harpin solutions is protein solubility and stability.

It would be desirable to identify synthetic and derivative harpin peptides that are readily soluble in aqueous solution, stable, resistant to chemical degradation, and effective in inducing active plant responses that include, among others, enhanced plant growth and production, as well as resistance to abiotic and biotic stressors.

The present invention is directed to overcoming these and other limitations in the art.

SUMMARY OF THE INVENTION

A first aspect of the invention relates to an isolated peptide comprising the amino acid sequence of: J-X-X-X-J-J-X-X-X-J-J-X-X-X-J-J  (SEQ ID NO: 1) wherein the peptide is free of cysteine and methionine; each X at positions 2, 3, 7, 8, 12, and 13 is optional and, when present, is any amino acid; each X at positions 4, 9, and 14 is any amino acid; one to three of the J residues at positions 1, 5, 6, 10, 11, 15, and 16 is a non-hydrophobic amino acid or A, and all other of the J residues are L, I, V, or F, and the peptide induces an active plant response, but does not induce a hypersensitive response, when applied to plant tissue.

A second aspect of the invention relates to an isolated peptide having the amino acid sequence of: XXGISEKXXXXXXXXXXXXXXXX  (SEQ ID NO: 2, modified P1/P4 consensus), wherein

-   -   X at position 1 is optional and can be S, N, D, isoD, G, A, or         S;     -   X at position 2 is optional and can be Q, E, g-glutamate, G, A,         or S;     -   X at position 8 is Q, E, g-glutamate, G, A, or S;     -   X at position 9 is M, L, I, F, or V, or a non-hydrophobic amino         acid;     -   X at position 10 is optional and can be D or isoD;     -   X at position 11 is Q, E, g-glutamate, G, A, or S;     -   X at position 12 is M, L, I, or F, or a non-hydrophobic amino         acid;     -   X at position 13 is M, L, or I, or a non-hydrophobic amino acid;     -   X at position 14 is optional and can be any hydrophilic amino         acid, preferably S, T, D, isoD, K, or Q, and optionally A or C;     -   X at position 15 is Q, E, g-glutamate, G, A, S, K, or I;     -   X at position 16 is M, L, I, V, or F, or a non-hydrophobic amino         acid;     -   X at position 17 is M, L, I, A, or V, or a non-hydrophobic amino         acid;     -   X at position 18 is Q, E, g-glutamate, G, A, S, M, T, or K;     -   X at position 19 is A, D, isoD, S, V, T, K, R, E, H, or G;     -   X at position 20 is M, L, or I;     -   X at position 21 is M, L, I, V, S, or F, or a non-hydrophobic         amino acid other than serine;     -   X at position 22 is Q, E, g-glutamate, G, A, S;     -   X at position 23 is P, Q, E, g-glutamate, G, A, or S; and         wherein at least one of the residues at positions 9, 12, 13, 16,         17, and 20 is a non-hydrophobic amino acid, or the residue at         position 21 is a non-hydrophobic amino acid other than serine;         and         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

A third aspect of the invention relates to an isolated peptide having the amino acid sequence of: SXGISEKXXDXXXXXXXXAXXXP  (SEQ ID NO:3, modified P4 consensus), wherein

-   -   X at position 2 is Q, E, g-glutamate, G, A, or S;     -   X at position 8 is Q, E, g-glutamate, G, A, or S;     -   X at position 9 is M, S, L, A, I, V, or F, or a non-hydrophobic         amino acid other than serine;     -   X at position 11 is Q, E, g-glutamate, G, A, or S;     -   X at position 12 is L, I, or F, or a non-hydrophobic amino acid;     -   X at position 13 is L, A, I, V, or F, or a non-hydrophobic amino         acid;     -   X at position 14 is any hydrophilic amino acid;     -   X at position 15 is Q, E, g-glutamate, G, A, S, K, or I;     -   X at position 16 is L, A, I, V, M, or F, or a non-hydrophobic         amino acid;     -   X at position 17 is M, I, S, or F, or a non-hydrophobic amino         acid other than serine;     -   X at position 18 is Q, E, g-glutamate, G, A, or S;     -   X at position 20 is M, L, I, V, or F, or a non-hydrophobic amino         acid;     -   X at position 21 is M, L or F, or a non-hydrophobic amino acid;         and     -   X at position 22 is Q, E, g-glutamate, G, A, or S,         wherein one of the residues at positions 9, 12, 13, 16, 20, and         21 is a non-hydrophobic amino acid or A, or the residue at         position 17 is a non-hydrophobic amino acid other than serine;         and wherein the peptide induces an active plant response, but         does not induce a hypersensitive response, when applied to plant         tissue.

A fourth aspect of the invention relates to an isolated peptide having the amino acid sequence of: XXGISEKXJDXJJTXJJXAJJXX  (SEQ ID NO: 4, modified P1 consensus), wherein

-   -   X at position 1 is N, D, isoD, G, A, or S;     -   X at position 2 is Q, E, g-glutamate, G, A, or S;     -   X at position 8 is Q, E, g-glutamate, G, A, or S;     -   X at position 11 is Q, E, g-glutamate, G, A, or S;     -   X at position 15 is Q, E, g-glutamate, G, A, or S;     -   X at position 18 is M, T, K, E, g-glutamate, G, A, or S;     -   X at position 22 is Q, E, g-glutamate, G, A, or S;     -   X at position 23 is Q, E, g-glutamate, G, A, or S;         J at positions 9, 12, 13, 16, 17, 20, and 21 are hydrophobic         amino acids selected from L, V, I, and F, except that one of the         amino acids at these positions is a non-hydrophobic amino acid         or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

A fifth aspect of the invention relates to an isolated peptide having the amino acid sequence of: (i) KPXDSXSXJAKJJSXJJXSJJX  (SEQ ID NO:5, modified P15b/P20 consensus), wherein

-   -   X at position 3 is N, D, or isoD;     -   X at position 6 is Q, E, g-glutamate, G, A, or S;     -   X at position 8 is N, D, or isoD;     -   X at position 15 is optional and can be any amino acid;     -   X at position 18 is M, E, g-glutamate, G, A, S, T, or K;     -   X at position 22 is optional and can be Q, E, g-glutamate, G, A,         or S; and         J at positions 9, 12, 13, 16, 17, 20, and 21 are hydrophobic         amino acids selected from L, V, I, and F, except that at least         one of the amino acids at these positions is a non-hydrophobic         amino acid or         A;     -   or         (ii) JAKJJSXJJXSJJX  (SEQ ID NO: 6, modified P15/20 min         consensus), wherein     -   X at position 7 is optional and can be any amino acid;     -   X at position 10 is M, E, g-glutamate, G, A, S, T, or K;     -   X at position 14 is optional and can be Q, E, g-glutamate, G, A,         or S; and         J at positions 1, 4, 5, 8, 9, 12, and 13 are hydrophobic amino         acids selected from L, V, I, and F, except that at least one of         the amino acids at these positions is a non-hydrophobic amino         acid or A;         and         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

A sixth aspect of the invention relates to an isolated peptide having the amino acid sequence of: PSPJTXJJXXJJGXJJXAXN  (SEQ ID NO: 7, modified P6/6a consensus), wherein

-   -   X at position 6 is Q, E, g-glutamate, G, A, or S;     -   X at position 9 is M, E, g-glutamate, G, A, S, T, or K;     -   X at position 10 is H or N;     -   X at position 14 is E, g-glutamate, D, or isoD;     -   X at position 17 is Q, E, g-glutamate, G, A, or S;     -   X at position 19 is Q, E, g-glutamate, G, A, or S; and         J at positions 4, 7, 8, 11, 12, 15, and 16 are hydrophobic amino         acids selected from L, V, I, M, and F, except that at least one         of the amino acids at these positions is a non-hydrophobic amino         acid or A; wherein the peptide induces an active plant response,         but does not induce a hypersensitive response, when applied to         plant tissue.

A seventh aspect of the invention relates to an isolated peptide having the amino acid sequence of: (i) XXXXXXJXXJJXXJJXJJK  (SEQ ID NO: 8, modified P14d consensus), wherein

-   -   X at position 1 can be: Q, N, D, E, g-glutamate, isoD, or S;     -   X at position 2 can be: D, E, g-glutamate, isoD;     -   X at position 3 can be: P, D, E, isoD, or g-glutamate;     -   X at position 4 can be M, A, S, D, E, isoD, or g-glutamate     -   X at position 5 can be Q, E, or g-glutamate;     -   X at position 6 can be A, E, or g-glutamate;     -   X at position 8 can be M, L, E, Q, D, N, G, A, S, isoD, or         g-glutamate;     -   X at position 9 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 12 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 13 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 16 can be K, Q, N, E, D, R, G, A, or S; and         J at positions 7, 10, 11, 14, 15, 17, and 18 are hydrophobic         amino acids selected from L, V, I, and F, except that at least         one of the amino acids at these positions is a non-hydrophobic         amino acid or A; or         (ii) JXXJJXXJJXJJK  (SEQ ID NO: 9, modified P14d min consensus),         wherein     -   X at position 2 can be M, L, E, Q, D, N, G, A, S, isoD, or         g-glutamate;     -   X at position 3 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 6 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 7 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 10 can be K, Q, N, E, D, R, G, A, or S; and         J at positions 1, 4, 5, 8, 9, 11, and 12 are hydrophobic amino         acids selected from L, V, I, and F, except that at least one of         the amino acids at these positions is a non-hydrophobic amino         acid or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

An eighth aspect of the invention relates to an isolated peptide having the amino acid sequence of: (i) JXXJJXJJXXJJ  (SEQ ID NO: 10, modified P25 consensus) wherein

-   -   X at position 2 can be Q, N, E, g-glutamate, D, isoD, T, S, A,         or G;     -   X at position 3 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 6 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 9 can be E, g-glutamate, D, isoD, Q, N, T, S, A,         or G;     -   X at position 10 can be A, G, S, T, E, g-glutamate, D, isoD, Q,         or N; and         J at positions 1, 4, 5, 7, 8, 10, and 11 are hydrophobic amino         acids selected from L, V, I, F, and M, except that at least one         of the amino acids at these positions is a non-hydrophobic amino         acid or A;         or         (ii) JXXJJXXJJXJJXXJJ  (SEQ ID NO: 11, modified P25 consensus)         wherein     -   X at position 2 can be T, S, A, G, D, isoD, E, g-glutamate, Q,         or N;     -   X at position 3 can be G, T, S, A, D, isoD, E, g-glutamate, Q,         or N;     -   X at position 6 can be Q, N, E, g-glutamate, D, isoD, T, S, A,         or G;     -   X at position 7 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 10 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 13 can be E, g-glutamate, D, isoD, Q, N, T, S, A,         or G;     -   X at position 14 can be A, G, S, T, E, g-glutamate, D, isoD, Q,         or N;         J at positions 1, 4, 5, 8, 9, 11, 12, and 15 are hydrophobic         amino acids selected from L, V, I, F, and M, except that at         least one of the amino acids at these positions is a         non-hydrophobic amino acid or A; and J at position 16 is         optional and a hydrophobic amino acid selected from L, V, I, and         F;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

A ninth aspect of the invention relates to an isolated peptide comprising the amino acid sequence of: (i) XXXXXXXXXXXJXXJJXXJJXXJJXXX  (SEQ ID NO: 12, modified P17/18), wherein

-   -   X at position 1 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 2 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 3 can be any amino acid, but preferably P, Q, S,         E, g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 4 can be any amino acid, but preferably I, Q, S,         E, g-glutamate, A, T, G, D, N, isoD, K, or R;     -   X at position 5 can be any amino acid, but preferably D, isoD,         S, E, g-glutamate, A, T, G, N, Q, K, or R;     -   X at position 6 can be any amino acid, but preferably R, Q, S,         E, g-glutamate, A, T, G, D, isoD, N, or K;     -   X of position 7 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 8 can be any amino acid, but preferably T, Q, S,         E, g-glutamate, A, G, D, isoD, N, K, or R;     -   X at position 9 can be any amino acid, but preferably I, Q, S,         E, g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 10 can be any amino acid, but preferably E,         g-glutamate, Q, S, A, T, G, D, isoD, N, K, or R;     -   X at position 11 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 13 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 14 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 17 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 18 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 21 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 22 can be any amino acid, but preferably S, A, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 25 can be any amino acid, but preferably S, A, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 26 can be any amino acid, but preferably P, S, A,         T, G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 27 can be any amino acid, but preferably Q, S, A,         T, G, D, isoD, E, g-glutamate, N, K, or R;         J at positions 12, 15, 16, 19, 20, 23, and 24 are hydrophobic         amino acids selected from L, V, I, F, and M, except that at         least one of the amino acids at these positions is a         non-hydrophobic amino acid or A; or         (ii) JXXJJXXJJXXJJ  (SEQ ID NO: 13, modified P17/18 min         consensus), wherein     -   X at position 2 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 3 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 6 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 7 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 10 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 11 can be any amino acid, but preferably S, A, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R; and         J at positions 1, 4, 5, 8, 9, 12, and 13 are hydrophobic amino         acids selected from L, V, I, F, and M, except that at least one         of the amino acids at these positions is a non-hydrophobic amino         acid or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

A tenth aspect of the invention relates to an isolated peptide comprising the amino acid sequence of: XJXXJJXJJXXJJ  (SEQ ID NO: 14, modified P19 consensus), wherein

-   -   X at position 1 is optional and can be L, I, V, F, or M;     -   X at position 3 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 4 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 7 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 10 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 11 can be any amino acid, but preferably R, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or K; and         J at positions 2, 5, 6, 8, 9, 12, and 13 are hydrophobic amino         acids selected from L, V, I, F, and M, except that at least one         of the amino acids at these positions is a non-hydrophobic amino         acid or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

An eleventh aspect of the invention relates to an isolated peptide that includes the amino acid sequence of: Z₁-LLXLFXXIL-Z₂  (SEQ ID NO: 126, P3 minimum) wherein

-   -   X at position 3 is any hydrophilic amino acid, preferably K, A,         S, T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 6 is any hydrophilic amino acid, preferably K, A,         S, T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 7 is any hydrophilic amino acid, preferably K, A,         S, T, G, D, isoD, E, g-glutamate, Q, N, or R; and     -   wherein one of Z₁ and Z₂ is present, but preferably not both,         with Z₁ comprising LXX- where each X is a hydrophilic amino         acid, preferably K, A, S, T, G, D, isoD, E, g-glutamate, Q, N,         or R, and with Z₂ comprising -XXLF where each X is a hydrophilic         amino acid, preferably K, A, S, T, G, D, isoD, E, g-glutamate,         Q, N, or R.

A twelfth aspect of the invention relates to an isolated peptide that includes the amino acid sequence of: L-X-X-(L/I)-(L/I)-X-X-(L/I/V)-(L/I/V) (SEQ ID NO: 116), wherein the peptide is free of cysteine and methionine; each X at positions 2, 3, 6, 7 is any amino acid; and the peptide induces an active plant response, but does not induce a hypersensitive response, when applied to plant tissue.

A thirteenth aspect of the invention relates to a fusion protein that includes one of the peptides of the first through twelfth aspects of the invention along with one or more of a purification tag, a solubility tag, or a second peptide according to one of the first through twelfth aspects of the invention.

A fourteenth aspect of the invention relates to an isolated peptide selected from the group consisting of DVGQLIGELIDRGLQ (SEQ ID NO: 15), GDVGQLIGELIDRGLQSVLAG (SEQ ID NO: 16), SSRALQEVIAQLAQELTHN (SEQ ID NO: 17), or GLEDIKAALDTLIHEKLG (SEQ ID NO: 18). Also encompassed by this aspect of the invention are fusion proteins that include one of these peptides along with one or more of a purification tag, a solubility tag, or a second peptide according to one of the first through twelfth and fourteenth aspects of the invention.

A fifteenth aspect of the invention relates to a composition that includes one or more peptides or fusion proteins according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, or fourteenth aspects of the invention, and a carrier.

A sixteenth aspect of the invention relates to a method of imparting disease resistance to plants. This method includes: applying an effective amount of an isolated peptide or fusion protein according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to impart disease resistance.

A seventeenth aspect of the invention relates to a method of enhancing plant growth. This method includes: applying an effective amount of an isolated peptide or fusion protein according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to enhance plant growth.

An eighteenth aspect of the invention relates to a method of increasing a plant's tolerance and resistance to biotic stressors. This method includes: applying an effective amount of an isolated peptide or fusion protein according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to increase the plant's tolerance and resistance to biotic stress factors selected from the group consisting of pests such as insects, arachnids, nematodes, weeds, and combinations thereof.

A nineteenth aspect of the invention relates to a method of increasing a plant's tolerance to abiotic stress. This method includes: applying an effective amount of an isolated peptide or fusion protein according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to increase the plant's tolerance to abiotic stress factors selected from the group consisting of salt stress, water stress (including drought and flooding), ozone stress, heavy metal stress, cold stress, heat stress, nutritional stress (phosphate, potassium, nitrogen deficiency) and combinations thereof.

A twentieth aspect of the invention relates to a method imparting desiccation resistance to cuttings removed from ornamental plants. This method includes: applying an isolated peptide or fusion protein according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant or the locus where the plant is growing, wherein said applying is effective to impart desiccation resistance to cuttings removed from the ornamental plant.

A twenty-first aspect of the invention relates to a method of imparting post-harvest disease or post-harvest desiccation resistance to a fruit or vegetable. This method includes: applying an effective amount of an isolated peptide or fusion protein according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant containing a fruit or vegetable or the locus where the plant is growing; or applying an effective amount of the isolated peptide or the composition to a harvested fruit or vegetable, wherein said applying is effective to impart post-harvest disease resistance or desiccation resistance to the fruit or vegetable.

A twenty-second aspect of the invention relates to a method of enhancing the longevity of fruit or vegetable ripeness. This method includes: applying an effective amount of an isolated peptide or fusion protein according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant containing a fruit or vegetable or the locus where the plant is growing; or applying an effective amount of the isolated peptide or the composition to a harvested fruit or vegetable, wherein said applying is effective to enhance the longevity of fruit or vegetable ripeness.

A twenty-third aspect of the invention relates to a method of modulating one or more biological signaling processes of a plant. This method includes: applying an effective amount of an isolated peptide according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a composition according to the fifteenth aspect of the invention to a plant or the locus where the plant is growing, wherein said applying is effective in initiating one or more biochemical signaling processes.

A twenty-fourth aspect of the invention relates to a DNA construct including a first nucleic acid molecule encoding a peptide according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth or fourteenth aspects of the invention or a fusion polypeptide containing the same; and a promoter-effective nucleic acid molecule operably coupled to the first nucleic acid molecule. This aspect of the invention also encompasses a recombinant expression vector containing the DNA construct, a recombinant host cell containing the DNA construct, as well as transgenic plants or plant seeds that include a recombinant plant cell of the invention (which contains the DNA construct).

A twenty-fifth aspect of the invention relates to a method of imparting disease resistance to plants, enhancing plant growth, imparting tolerance and resistance to biotic stressors, imparting tolerance to abiotic stress, or modulating plant biochemical signaling. This method includes providing a transgenic plant transformed with a DNA construct according to the twenty-fourth aspect of the invention; and growing the plant under conditions effective to permit the DNA construct to express the peptide or the fusion polypeptide to impart disease resistance, enhance plant growth, impart tolerance and resistance to biotic stressors, impart tolerance to abiotic stress, or modulate biochemical signaling to the transgenic plant.

A twenty-sixth aspect of the invention relates to a method of imparting desiccation resistance to cuttings removed from ornamental plants, imparting post-harvest disease or post-harvest desiccation resistance to a fruit or vegetable, or enhancing the longevity of fruit or vegetable ripeness. The method includes providing a transgenic plant transformed with a DNA construct according to the twenty-fourth aspect of the invention; and growing the plant under conditions effective to permit the DNA construct to express the peptide or the fusion polypeptide to impart desiccation resistance to cuttings removed from a transgenic ornamental plant, impart post-harvest disease resistance or desiccation resistance to a fruit or vegetable removed from the transgenic plant, or enhance longevity of ripeness for a fruit or vegetable removed from the transgenic plant.

A twenty-seventh aspect of the invention relates to a method of imparting disease resistance to plants, enhancing plant growth, imparting tolerance and resistance to biotic stressors, imparting tolerance to abiotic stress, or modulating biochemical signaling. This method includes providing a transgenic plant seed transformed with a DNA construct according to the twenty-fourth aspect of the invention; planting the transgenic plant seed in soil; and propagating a transgenic plant from the transgenic plant seed to permit the DNA construct to express the peptide or the fusion polypeptide to impart disease resistance, enhance plant growth, impart tolerance to biotic stress and resistance to biotic stressors, or impart tolerance to abiotic stress.

A twenty-eighth aspect of the invention relates to a method of imparting desiccation resistance to cuttings removed from ornamental plants, imparting post-harvest disease or post-harvest desiccation resistance to a fruit or vegetable, or enhancing the longevity of fruit or vegetable ripeness. The method includes providing a transgenic plant seed transformed with a DNA construct according to the twenty-fourth aspect of the invention; planting the transgenic plant seed in soil; and propagating a transgenic plant from the transgenic plant seed to permit the DNA construct to express the peptide or the fusion polypeptide to impart desiccation resistance to cuttings removed from a transgenic ornamental plant, impart post-harvest disease resistance or desiccation resistance to a fruit or vegetable removed from the transgenic plant, or enhance longevity of ripeness for a fruit or vegetable removed from the transgenic plant.

By providing peptides that do not elicit a hypersensitive response but elicit other active plant responses, including, among others, peroxide production, growth enhancement, and resistance to biotic and abiotic stress, where such peptides desirably exhibit improved solubility, stability, resistance to chemical degradation, or a combination of these properties, it will afford growers with greater flexibility in preparing, handling, and delivering to plants in their fields or greenhouses effective amounts of compositions containing these HR-negative peptides. Simplifying the application process for growers will lead to greater compliance and, thus, improved results with respect to one or more of disease resistance, growth enhancement, tolerance and resistance to biotic stressors, tolerance to abiotic stress, desiccation resistance for cuttings removed from ornamental plants, post-harvest disease resistance or desiccation resistance to fruit or vegetables harvested from plants, and/or improved longevity of fruit or vegetable ripeness for fruit or vegetables harvested from plants. These and other benefits are described herein.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the invention relates to novel peptides that possess the ability to induce an active plant response, but not a hypersensitive response, that afford one or more of the following attributes: modified biochemical signaling; enhanced growth; pathogen resistance; and/or biotic or abiotic stress resistance.

As used herein, naturally occurring amino acids are identified throughout by the conventional three-letter and/or one-letter abbreviations, corresponding to the trivial name of the amino acid, in accordance with the following list: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), and Valine (Val, V). The abbreviations are accepted in the peptide art and are recommended by the IUPAC-IUB commission in biochemical nomenclature. Naturally occurring variations of amino acids include, without limitation, gamma-glutamate (g-Glu) and isoaspartate (iso-Asp or isoD).

The term “amino acid” further includes analogues, derivatives, and congeners of any specific amino acid referred to herein, as well as C-terminal or N-terminal protected amino acid derivatives (e.g., modified with an N-terminal, side chain, or C-terminal protecting group, including but not limited to acetylation, formylation, methylation, amidation, esterification, PEGylation, and addition of lipids). Non-naturally occurring amino acids are well known and can be introduced into peptides of the present invention using solid phase synthesis as described below. Furthermore, the term “amino acid” includes both D- and L-amino acids. Hence, an amino acid which is identified herein by its name, three letter or one letter symbol and is not identified specifically as having the D or L configuration, is understood to assume any one of the D or L configurations. In one embodiment, a peptide comprises all L-amino acids.

In certain embodiments, peptides are identified to “consist of” a recited sequence, in which case the peptide includes only the recited amino acid sequence(s) without any extraneous amino acids at the N- or C-terminal ends thereof. To the extent that a recited sequence is in the form of a consensus sequence where one or more of the denoted X or Xaa residues can be any of one or more amino acids, then multiple peptide sequences are embraced by a peptide consisting of such a recited sequence.

In certain other embodiments, peptides are identified to “consist essentially of” a recited sequence, in which case the peptide includes the recited amino acid sequence(s) optionally with one or more extraneous amino acids at the N- and/or C-terminal ends thereof, which extraneous amino acids do not materially alter one or more of the following properties: (i) the ability of the peptide to induce an active plant response, (ii) solubility of the peptide in water or aqueous solutions, (iii) stability of the peptide dissolved in water or aqueous solution at 50° C. over a period of time (e.g., 3 weeks), (iv) resistance of the peptide to chemical degradation in the presence of an aqueous buffered solution that includes a biocidal agent (e.g., Proxel®GXL) at 50° C. over a period of time (e.g., 3 weeks); and (v) the inability of the peptide to induce a hypersensitive response upon infiltration or application to plants.

Briefly, the stability and resistance to chemical degradation of peptides can be assessed as follows using peptide samples having an initial purity of at least about 80%, at least about 82%, at least about 84%, at least about 86%, at least about 88%, at least about 90%, at least about 92%, at least about 94%, at least about 96%, or at least about 98%. For water stability, the peptide is dissolved directly in de-ionized water. For chemical degradation tests, the peptide is dissolved in an aqueous solution containing 50 mM pH buffer and 0.25% Proxel GXL. Exemplary pH buffers include, without limitation: (i) Citrate pH 5.6; (ii) MES pH 6.2; (iii) MOPS pH 6.5; (iv) imidazole pH 7.0; (v) Citrate pH 7.2; (vi) EDDS, pH 7.3; (vii) EDTA pH 8.0; (viii) sodium phosphate pH 8.0; or (ix) TES pH 8.0. Peptides are first dissolved in the aqueous solution at a concentration of 0.5 mg/ml. The samples are incubated at 50° C. to allow for accelerated degradation. An initial sample of the peptide is removed, diluted 10× with water, and analyzed by reverse-phase HPLC. Briefly, 20 μl of the sample is injected into the solvent flow of an HPLC instrument and analyzed on a C18 HPLC column (YMC ProPack C18, YMC, Japan, or C18 Stablebond, Agilent Technologies, USA) using either a triethylamine phosphate in water/acetonitrile gradient or a 0.1% TFA in water/0.1% TFA in acetonitrile gradient to separate different peptide species. Eluting peptides are monitored by UV absorbance at 218 nm and quantified based on the area under the peak. The area under the peak for the initial peptide sample is treated as the standard for relative quantification in subsequent runs. At regular intervals (e.g., 1, 3, 7, 10, 14, 17, and 21 days), each peptide sample is surveyed and analyzed by HPLC as described above. If necessary to observe degradation (i.e., where the peptide exhibits a high degree of chemical stability), this protocol can be extended by several weeks to observe degradation. The quantification of subsequent peptide runs is expressed as a percentage of the original (day 0) HPLC result.

A peptide that is at least partially soluble in water or aqueous solution exhibits a solubility of greater than 0.1 mg/ml, preferably at least about 1.0 mg/ml, at least about 2.0 mg/ml, at least about 3.0 mg/ml, or at least about 4.0 mg/ml. In certain embodiments, the peptide exhibits high solubility in water or aqueous solution, with a solubility of at least about 5.0 mg/ml, at least about 10.0 mg/ml, at least about 15.0 mg/ml, or at least about 20 mg/ml.

A peptide that is stable in water or aqueous solution exhibits at least about 66%, at least about 68%, at least about 70%, at least about 72%, at least about 74%, at least about 76%, at least about 78%, at least about 80%, at least about 82%, at least about 84%, at least about 86%, at least about 88%, or at least about 90% of the original peptide concentration over the designated period of time incubated at 50° C. In certain embodiments, the designated period of time is 3 days, 7 days, 14 days, 21 days, 28 days, one month, two months, or three months.

A peptide that is resistant to chemical degradation exhibits at least about 66%, at least about 68%, at least about 70%, at least about 72%, at least about 74%, at least about 76%, at least about 78%, at least about 80%, at least about 82%, at least about 84%, at least about 86%, at least about 88%, or at least about 90% of the original peptide concentration over the designated period of time incubated at 50° C. In certain embodiments, the designated period of time is 3 days, 7 days, 14 days, 21 days, 28 days, one month, two months, three months, or four months. Four months of stability at 50° C. is roughly equivalent to 2 years of stability at room temperature.

A property of a peptide to elicit a hypersensitive response, or not, upon infiltration or application of the peptide to plant tissues can be measured by applying the peptide in dry powder form or in solution form to a plant, particularly though not exclusively a plant leaf. Application rates include 1-500 ug/ml for liquid solution and 0.0001-0.5% (w/w for powder application. Exemplary application of the peptide in solution form is described in the accompanying Examples. Plants are considered HR-positive (“HR+”) if they exhibit wide-spread macroscopic cell death visible to the naked eye, accompanied by wilting and browning of the affected tissue within 48 hours. Plants are considered HR-negative (“HR−”) if they exhibit no discernible wilting or tissue death observable by naked eye. It is possible that an HR− peptide could cause the death of a small proportion of cells in treated tissue which is not observable by naked eye.

In certain embodiments, material alteration of the one or more properties is intended to mean that there is less than 20% variation, less than 15% variation, less than 10% variation, or less than 5% variation in a recited property when comparing a peptide possessing the one or more extraneous amino acids to an otherwise identical peptide lacking the one or more extraneous amino acids. In certain embodiments, the number of extraneous amino acids at the N- or C-terminal ends is up to 20 amino acids at one or both ends, up to 15 amino acids at one or both ends, up to 10 amino acids at one or both ends, up to 7 amino acids at one or both ends, up to 5 amino acids at one or both ends, or up to 3 amino acids at one or both ends. Further, to the extent that a recited sequence is in the form of a consensus sequence where one or more of the denoted X or Xaa residues can be any of one or more amino acids, then multiple peptide sequences are embraced by the peptide consisting essentially of such a recited sequence, without regard to additional variations of such sequences that are afforded by the presence of extraneous amino acids at the N- and/or C-terminal ends thereof.

In various embodiments of the invention, the disclosed peptides may include a hydrophilic amino acid sequence, e.g., at either the N-terminal or C-terminal end of a designated peptide sequence. The hydrophilic amino acid sequence is at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, or at least 10 amino acids in length, and includes amino acid residues that contribute to a hydrophilic property of the amino acid sequence that is adjacent to the amino acid sequence of the designated peptide (i.e., the peptide that induces an active plant response). Different methods have been used in the art to calculate the relative hydrophobicity/hydrophilicity of amino acid residues and proteins (Kyte et al., “A Simple Method for Displaying the Hydropathic Character of a Protein,” J. Mol. Biol. 157: 105-32 (1982); Eisenberg D, “Three-dimensional Structure of Membrane and Surface Proteins,” Ann. Rev. Biochem. 53: 595-623 (1984); Rose et al., “Hydrogen Bonding, Hydrophobicity, Packing, and Protein Folding,” Annu. Rev. Biomol. Struct. 22: 381-415 (1993); Kauzmann, “Some Factors in the Interpretation of Protein Denaturation,” Adv. Protein Chem. 14: 1-63 (1959), which are hereby incorporated by reference in their entirety). Any one of these hydrophobicity scales can be used for the purposes of the present invention; however, the Kyte-Doolittle hydrophobicity scale is perhaps the most often referenced scale. These hydropathy scales provide a ranking list for the relative hydrophobicity of amino acid residues. For example, amino acids that contribute to hydrophilicity include Arg (R), Lys (K), Asp (D), Glu (E), Gln (Q), Asn (N), and His (H) as well as, albeit to a lesser extent, Ser (S), Thr (T), Gly (G), Pro (P), Tyr (Y), and Trp (W). For example, polyglutamate sequences can be used to enhance solubility of proteins and other drug molecules (Lilie et al, Biological Chemistry 394(8):995-1004 (2013); Li et al., Cancer Research 58: 2404-2409 (1998)), each of which is hereby incorporated by reference in its entirety).

The “hydropathy index” of a protein or amino acid sequence is a number representing its average hydrophilic or hydrophobic properties. A negative hydropathy index defines the hydrophilicity of the amino acid sequence of interest. The hydropathy index is directly proportional to the hydrophilicity of the amino acid sequence of interest; thus, the more negative the index, the greater its hydrophilicity. In certain embodiments, the added hydrophilic amino acid sequence described above has a hydropathy index of less than 0, −0.4, −0.9, −1.3, −1.6, −3.5, −3.9, or −4.5. In certain embodiments, the resulting entire peptide will have a hydropathy index of less than 0.3, 0.2, 0.1, or 0.0, preferably less than −0.1, −0.2, −0.3, −0.4, more preferably less than −0.5, −0.6, −0.7, −0.8, −0.9, or −1.0.

In the peptides of the present invention, amino acids that contribute to a hydrophilic hydropathy index, for either the peptide as a whole or the added hydrophilic amino acid sequence, include Arg (R), Lys (K), Asp (D), Glu (E), Gln (Q), Asn (N), His (H), Ser (S), Thr (T), Gly (G), Pro (P), Tyr (Y), and Trp (W). Of these, Asp (D), Glu (E), Gln (Q), Asn (N) or their variants are preferred. Exemplary variants include g-glutamate for Glu and isoaspartic acid (or isoD) for Asp.

As used herein, in this and in other aspects of the invention, the term “hydrophobic amino acid” is intended to refer to an amino acid that contributes hydrophobicity to the hydropathy index of a designated amino acid sequence. Amino acids that contribute to a hydrophobic hydropathy index, for either the peptide as a whole or a particular amino acid sequence thereof, include Ile (I), Val (V), Leu (L), Phe (F), Cys (C), Met (M), and Ala (A). In certain embodiments, the term “hydrophobic amino acid” may refer to any one of Ile (I), Val (V), Leu (L), Phe (F), Cys (C), Met (M), and Ala (A); or, alternatively, to any one of Ile (I), Val (V), Leu (L), Phe (F), and Ala (A). In certain other embodiments, the term “hydrophobic amino acid” may refer to one of Ile (I), Val (V), Leu (L), and Phe (F).

As used herein, the term “non-hydrophobic amino acid” is intended to mean an amino acid that is hydrophilic (or not hydrophobic) on one of the above-identified hydrophobicity scales. This term generally refers to those amino acids that contribute to a hydrophilic hydropathy index for either the peptide as a whole or the added hydrophilic amino acid sequence.

In one aspect of the invention, the peptide includes the amino acid sequence of: J-X-X-X-J-J-X-X-X-J-J-X-X-X-J-J  (SEQ ID NO: 1) wherein the peptide is free of cysteine and methionine, each X at positions 2, 3, 7, 8, 12, and 13 is optional and, when present, is any amino acid, each X residue at positions 4, 9, and 14 is any amino acid, one to three of the J residues at positions 1, 5, 6, 10, 11, 15, and 16 is a non-hydrophobic amino acid or A (preferably, when A is present, it is at one of positions 1, 5, 6, 10, 15, or 16), and all other of the J residues are L, I, V, or F, (preferably L, I, or V); and wherein the peptide induces an active plant response, but does not induce a hypersensitive response, when applied to plant tissue.

In certain embodiments, the peptide does not comprise or consist of the amino acid sequence DVGQLIGELIDRGLQ (SEQ ID NO: 15), GDVGQLIGELIDRGLQSVLAG (SEQ ID NO: 16), SSRALQEVIAQLAQELTHN (SEQ ID NO: 17), or GLEDIKAALDTLIHEKLG (SEQ ID NO: 18). Each of these peptides is identified in Haapalainen et al., “Functional Mapping of Harpin HrpZ of Pseudomonas syringae Reveals the Sites Responsible for Protein Oligomerization, Lipid Interactions, and Plant Defence Induction,” Mol. Plant Pathol. 12(2):151-66 (2011), which is hereby incorporated by reference in its entirety.

In one embodiment, one to three of the J residues at positions 1, 5, 6, 10, 11, 15, and 16 is a non-hydrophobic amino acid, and all other are preferably L, I, V, or F. According to a particular embodiment, not more than two of the J residues at positions 1, 5, 6, 10, 11, 15, and 16 are non-hydrophobic. In another embodiment, not more than one of the J residues at positions 1, 5, 6, 10, 11, 15, and 16 is non-hydrophobic.

In one embodiment, not more than one of the J residues is A, and preferably the A residue is at one of positions 1, 5, 6, 10, 15, and 16; one or two of the remaining J residues is optionally a non-hydrophobic amino acid, and all other J residues are L, I, V, or F. In certain embodiments, not more than one of the J residues is A, and preferably the A residue is at one of positions 1, 5, 6, 10, 15, and 16; and all other J residues are L, I, V, or F.

In certain embodiments, the number of amino acids separating the residues at position 1 from positions 5 and 6, from positions 10 and 11, and from positions 15 and 16 can vary from one to three amino acids. In one embodiment, one of the X residues at positions 2 and 3 is not present, one of the X residues at positions 7 and 8 is not present, one of the X residues at positions 12 and 13 is not present, or two or more of the X residues at these positions is not present. For example, in one embodiment, one of the X residues at positions 2 and 3 and one of the X residues at positions 7 and 8 are not present. In another embodiment, the X residue at position 12, 13, or both, is not present. In another embodiment, one of the X residues at positions 2 and 3, one of the X residues at positions 7 and 8, and one of the X residues at positions 12 and 13 are not present.

In another embodiment, each of the X residues at positions 2, 3, 7, and 8 is present (i.e., the peptide includes three amino acids separating the residue at position 1 from the residues at positions 5 and 6, and the residues at positions 5 and 6 from the residues positions 10 and 11). In another embodiment, the X residue at position 12 is present or the X residues at positions 12 and 13 are present (i.e., the peptide includes two or three amino acids separating the residues at positions 10 and 11 from the residues at positions 15 and 16).

In the preceding paragraphs, the residue numbering refers to SEQ ID NO: 1, although because certain residues are optional, the actual position of J residues and intervening residues may differ in any one particular peptide.

The peptide length in this embodiment is less than 100 amino acids, or alternatively less than 90 amino acids, less than 80 amino acids, less than 70 amino acids, less than 60 amino acids, or less than about 50 amino acids. In certain embodiments, the peptide length is between 12 and about 50 amino acids in length.

In the embodiments described above, where X residues at each of positions 2, 3, 7, 8, 12, (when present) of SEQ ID NO: 1 can be any amino acid, in certain embodiments these residues are independently selected from the group of Arg (R), Lys (K), Asp (D), Glu (E), Gln (Q), Asn (N), Ser (S), Thr (T), Gly (G), isoaspartic acid (isoD), and g-glutamate, and each X residue at positions 4, 9, and 13 is independently selected from the group consisting of G, A, S, T, D, isoD, E, g-glutamate, Q, N, K, and R.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Exemplary peptides according to the first aspect of the invention comprise amino acid sequences identified in Table 1 below:

TABLE 1 Name Sequence SEQ ID NO: P14-22L, 26E QAGPQSANKTGNVDDANNQDPLQALEQLLEDLV 19 P14-22A, 26L QAGPQSANKTGNVDDANNQDPAQALLQLLEDLV 20 P14-22A, 26E QAGPQSANKTGNVDDANNQDPAQALEQLLEDLV 21 P14-22E, 26L QAGPQSANKTGNVDDANNQDPEQALLQLLEDLV 22 P14-22E, 26E QAGPQSANKTGNVDDANNQDPEQALEQLLEDLV 23 P14-22E, 26E-R QAGPQSANETGNVDDANNQDPEQALEQLLEDLVR 24 P14-22E, 26A QAGPQSANKTGNVDDANNQDPE_ALAQLLEDLV 25 P14-22L, 26A QAGPQSANKTGNVDDANNQDPLQALAQLLEDLV 26 P14-22A, 26A QAGPQSANKTGNVDDANNQDPAQALAQLLEDLV 27 P14-22L, 25-26A QAGPQSANKTGNVDDANNQDPLQAAAQLLEDLV 28 P14-22L, 28-29A QAGPQSANKTGNVDDANNQDPLQALLQAAEDLV 29 P14-22L, 32-33A QAGPQSANKTGNVDDANNQDPLQALLQLLEDAA 30 P14-22L, 26, 29A QAGPQSANKTGNVDDANNQDPLQALAQLAEDLV 31 P14-22L, 29, 32A QAGPQSANKTGNVDDANNQDPLQALLQLAEDAV 32 P14f-7D                   QDPAQADEQLLEDLVKLLK 33 P14f-10D                   QDPAQALEQDLEDLVKLLK 34 P14f-11D                   QDPAQALEQLDEDLVKLLK 35 P14f-14D                   QDPAQALEQLLEDDVKLLK 36 P14f-15D                   QDPAQALEQLLEDLDKLLK 37 P14f-17D                   QDPAQALEQLLEDLVKDLK 38 P14f-18D                   QDPAQALEQLLEDLVKLDK 39 P14f-7S                   QDPAQASEQLLEDLVKLLK 40 P14f-10S                   QDPAQALEQSLEDLVKLLK 41 P14f-11S                   QDPAQALEQLSEDLVKLLK 42 P14f-14S                   QDPAQALEQLLEDSVKLLK 43 P14f-15S                   QDPAQALEQLLEDLSKLLK 44 P14f-17S                   QDPAQALEQLLEDLVKSLK 45 P14f-18S                   QDPAQALEQLLEDLVKLSK 46

In certain embodiments, these peptides consist essentially of, or consist of, the amino sequence of one or more of SEQ ID NOS: 19-46.

Other exemplary peptides according to the first aspect of the invention comprise the amino acid sequences identified in Table 2 below:

TABLE 2 SEQ ID Name Sequence NO: P4-14S-13A SQGISEKQLDQLASQLIQALLQP 47 P4-14S-13D SQGISEKQLDQLDSQLIQALLQP 48 P4-14S-17D SQGISEKQLDQLLSQLDQALLQP 49 P4-14S-21D SQGISEKQLDQLLSQLIQALDQP 50 P4-d18 SQGISEKQLDQLLSQLI_ALLQP 51 P4-14S-9S SQGISEKQSDQLLSQLIQALLQP 52 P4-14S-9Y SQGISEKQYDQLLSQLIQALLQP 53 P4-14S-13Q SQGISEKQLDQLQSQLIQALLQP 54 P4-14S-16S SQGISEKQLDQLLSQSIQALLQP 55 P4-14S-20S SQGISEKQLDQLLSQLIQASLQP 56 P4-14S-9A SQGISEKQADQLLSQLIQALLQP 57 P4-14S-9D SQGISEKQDDQLLSQLIQALLQP 58 P4-14S-12D SQGISEKQLDQDLSQLIQALLQP 59 P4-14S-16A SQGISEKQLDQLLSQAIQALLQP 60 P4-14S-17S SQGISEKQLDQLLSQLSQALLQP 61 P4-d10, 14, 18 SQGISEKQL_QLL_QLI_ALLQP 62 P4-i21Q SQGISEKQLDQLLSQLIQAQLLQP 63 P4-i21H SQGISEKQLDQLLSQLIQAHLLQP 64 P4-i10A SQGISEKQLADQLLSQLIQALLQP 65 P4-i14A SQGISEKQLDQLLASQLIQALLQP 66 P4-i18A SQGISEKQLDQLLSQLIAQALLQP 67 P4-i10A, 14A, 18A SQGISEKQLADQLLASQLIAQALLQP 68

In certain embodiments, these peptides consist essentially of, or consist of, the amino sequence of one or more of SEQ ID NOS: 47-68.

Further exemplary peptides according to the first aspect of the invention comprise the amino acid sequences identified in Table 3 below:

TABLE 3 Name Sequence SEQ ID NO: P25min-7D SEEEEE DTGVLQKLLKILEAL 69 P25min-10D SEEEEELTGDLQKLLKILEAL 70 P25min-11D SEEEEELTGVDQKLLKILEAL 71 P25min-14D SEEEEELTGVLQKDLKILEAL 72 P25min-15D SEEEEELTGVLQKLDKILEAL 73 P25min-17D SEEEEELTGVLQKLLKDLEAL 74 P25min-18D SEEEEELTGVLQKLLKIDEAL 75 P25min-21D SEEEEELTGVLQKLLKILEAD 76 P25min-7S SEEEEE STGVLQKLLKILEAL 77 P25min-10S SEEEEELTGSLQKLLKILEAL 78 P25min-11S SEEEEELTGVSQKLLKILEAL 79 P25min-14S SEEEEELTGVLQKSLKILEAL 80 P25min-15S SEEEEELTGVLQKLSKILEAL 81 P25min-17S SEEEEELTGVLQKLLKSLEAL 82 P25min-18S SEEEEELTGVLQKLLKISEAL 83 P25min-21S SEEEEELTGVLQKLLKILEAS 84 In Table 3, the peptides include the solubility tag SEEEEE, indicated by italic print. Peptides comprising the sequences shown in Table 3 but lacking this specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain embodiments, these peptides consist essentially of, or consist of, the amino sequence of one or more of SEQ ID NOS: 69-84.

Peptides of the first aspect of the invention may also comprise the amino acid sequences identified in Table 4 below:

TABLE 4 Name Sequence SEQ ID NO: P18min-7D SEEEEE DAQLLAQLLKSLL 85 P18min-10D SEEEEELAQDLAQLLKSLL 86 P18min-11D SEEEEELAQLDAQLLKSLL 87 P18min-14D SEEEEELAQLLAQDLKSLL 88 P18min-15D SEEEEELAQLLAQLDKSLL 89 P18min-18D SEEEEELAQLLAQLLKSDL 90 P18min-19D SEEEEELAQLLAQLLKSLD 91 P18min-7S SEEEEE SAQLLAQLLKSLL 92 P18min-10S SEEEEELAQSLAQLLKSLL 93 P18min-11S SEEEEELAQLSAQLLKSLL 94 P18min-14S SEEEEELAQLLAQSLKSLL 95 P18min-15S SEEEEELAQLLAQLSKSLL 96 P18min-18S SEEEEELAQLLAQLLKSSL 97 P18min-19S SEEEEELAQLLAQLLKSLS 98 In Table 4, the peptides include the solubility tag SEEEEE, indicated by italic print. Peptides comprising the sequences shown in Table 4 but lacking this specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain embodiments, these peptides consist essentially of, or consist of, the amino sequence of one or more of SEQ ID NOS: 85-98.

In another embodiment of the first aspect of the invention, peptides comprise the amino acid sequences identified in Table 5 below:

TABLE 5 Name Sequence SEQ ID NO: P19min-7D SEEEEE DKALLKLIARLL 99 P19min-10D SEEEEELKADLKLIARLL 100 P19min-11D SEEEEELKALDKLIARLL 101 P19min-13D SEEEEELKALLKDIARLL 102 P19min-14D SEEEEELKALLKLDARLL 103 P19min-17D SEEEEELKALLKLIARDL 104 P19min-18D SEEEEELKALLKLIARLD 105 P19min-7S SEEEEE SKALLKLIARLL 106 P19min-10S SEEEEELKASLKLIARLL 107 P19min-11S SEEEEELKALSKLIARLL 108 P19min-13S SEEEEELKALLKSIARLL 109 P19min-14S SEEEEELKALLKLSARLL 110 P19min-17S SEEEEELKALLKLIARSL 111 P19min-18S SEEEEELKALLKLIARLS 112 In Table 5, the peptides include the solubility tag SEEEEE, indicated by italic print. Peptides comprising the sequences shown in Table 5 but lacking this specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain embodiments, these peptides consist essentially of, or consist of, the amino sequence of one or more of SEQ ID NOS: 99-112.

Another aspect of the invention relates to an isolated peptide comprising the amino acid sequence of one of SEQ ID NOS: 113, 114, 117-123, 127, 133-138, 140-142, 144, 145, 148-150, and 153-155, as shown in Table 6 below:

TABLE 6 SEQ ID Name Sequence NO: P14 QAGPQSANKTGNVDDANNQDPMQALMQLLEDLV 113 P14a ANNQDPMQALMQLLEDLV 114 P14-dc1 QAGPQSANKTGNVDDANNQDPMQALMQLLEDL 121 P14-dc2 QAGPQSANKTGNVDDANNQDPMQALMQLLED 122 P14-dc4 QAGPQSANKTGNVDDANNQDPMQALMQLL 123 P14-40 SEEEEELMQLLEDLV 127 P14-dN2 GPQSANKTGNVDDANNQDPMQALMQLLEDLV 117 P14-dN4 QSANKTGNVDDANNQDPMQALMQLLEDLV 118 P14-dN6 ANKTGNVDDANNQDPMQALMQLLEDLV 119 P14-dN8 KTGNVDDANNQDPMQALMQLLEDLV 120 P4-14S-13V SQGISEKQLDQLVSQLIQALLQP 133 P4-14S-13F SQGISEKQLDQLFSQLIQALLQP 134 P4-14S-16V SQGISEKQLDQLLSQVIQALLQP 135 P4-14S-17F SQGISEKQLDQLLSQLFQALLQP 136 P4-14S-20V SQGISEKQLDQLLSQLIQAVLQP 137 P4-14S-20F SQGISEKQLDQLLSQLIQAFLQP 138 P4-116 SQGISEKQLDQLLSQL 140 P4-117 SQGISEKQLDQLLSQ 141 P18-8 QQPIDRQTIEQMAQLLAQLL 142 P19-9 SEEEEEIGDNPLLKALLKLIA 144 P19-10 SEEEEEELLKALLKLIA 145 P15-62 KPNDSQSNIAKLISALI 148 P15-63 SEEEEEEIAKLISALI 149 P15-60 SEEEEEEEIAKLISALIESLL 150 P25-12 SEEEEELTGVLQKLLK_ILE 153 P25-13 SEEEEELTLTGVLQKLLKILE 154 P25-14 SEEEEELTLTGVLQKLLKIL 155 In Table 6, several peptides include the solubility tags S-polyE where the polyE segment contains from 3 to 7 Glu (E) residues, indicated by italic print. Peptides comprising the sequences shown in Table 6 but lacking this specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain embodiments, these peptides consist essentially of, or consist of, the amino sequence of one or more of SEQ ID NOS: 113, 114, 117-123, 127, 133-138, 140-142, 144, 145, 148-150, 153-159.

Another aspect of the invention relates to an isolated peptide having the amino acid sequence of: XXGISEKXXXXXXXXXXXXXXXX  (SEQ ID NO: 2, modified P1/P4 consensus), wherein

-   X at position 1 is optional and can be S, N, D, isoD, G, A, or S; -   X at position 2 is optional and can be Q, E, g-glutamate, G, A, or     S; -   X at position 8 is Q, E, g-glutamate, G, A, or S; -   X at position 9 is M, L, I, F, or V, or a non-hydrophobic amino     acid; -   X at position 10 is optional and can be D or isoD; -   X at position 11 is Q, E, g-glutamate, G, A, or S; -   X at position 12 is M, L, I, or F, or a non-hydrophobic amino acid; -   X at position 13 is M, L, or I, or a non-hydrophobic amino acid; -   X at position 14 is optional and can be any hydrophilic amino acid,     S, T, D, isoD, K, or Q, and optionally A or C; -   X at position 15 is Q, E, g-glutamate, G, A, S, K, or I; -   X at position 16 is M, L, I, V, or F, or a non-hydrophobic amino     acid; -   X at position 17 is M, L, I, A, or V, or a non-hydrophobic amino     acid; -   X at position 18 is Q, E, g-glutamate, G, A, S, M, T, or K; -   X at position 19 is A, D, isoD, S, V, T, K, R, E, H, or G; -   X at position 20 is M, L, or I; -   X at position 21 is M, L, I, V, S, or F, or a non-hydrophobic amino     acid other than serine; -   X at position 22 is Q, E, g-glutamate, G, A, S; -   X at position 23 is P, Q, E, g-glutamate, G, A, or S; and     wherein at least one of the residues at positions 9, 12, 13, 16, 17,     and 20 is a non-hydrophobic amino acid, or the residue at position     21 is a non-hydrophobic amino acid other than serine; and     wherein the peptide induces an active plant response, but does not     induce a hypersensitive response, when applied to plant tissue.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

One exemplary family of peptides according to this aspect of the invention have the amino acid sequence of: SXGISEKXXDXXXXXXXXAXXXP  (SEQ ID NO: 3, modified P4 consensus), wherein

-   X at position 2 is Q, E, g-glutamate, G, A, or S; -   X at position 8 is Q, E, g-glutamate, G, A, or S; -   X at position 9 is M, S, L, A, I, V, or F, or a non-hydrophobic     amino acid other than serine; -   X at position 11 is Q, E, g-glutamate, G, A, or S; -   X at position 12 is L, I, or F, or a non-hydrophobic amino acid; -   X at position 13 is L, A, I, V, or F, or a non-hydrophobic amino     acid; -   X at position 14 is any hydrophilic amino acid; -   X at position 15 is Q, E, g-glutamate, G, A, S, K, or I; -   X at position 16 is L, A, I, V, M, or F, or a non-hydrophobic amino     acid; -   X at position 17 is M, I, S, or F, or a non-hydrophobic amino acid     other than serine; -   X at position 18 is Q, E, g-glutamate, G, A, or S; -   X at position 20 is M, L, I, V, or F, or a non-hydrophobic amino     acid; -   X at position 21 is M, L or F, or a non-hydrophobic amino acid; and -   X at position 22 is Q, E, g-glutamate, G, A, or S;     wherein one of the residues at positions 9, 12, 13, 16, 20, and 21     is a non-hydrophobic amino acid or A, or the residue at position 17     is a non-hydrophobic amino acid other than serine; and wherein the     peptide induces an active plant response, but does not induce a     hypersensitive response, when applied to plant tissue. Preferably,     one to four, not more than three, not more than two, or exactly one     of the residues at positions 9, 12, 13, 16, 20, and 21 is a     non-hydrophobic amino acid, or the residue at position 17 is a     non-hydrophobic amino acid other than serine.

In certain embodiments, these peptides according to SEQ ID NO: 2 also meet the structural features defining the peptides of SEQ ID NO: 1, in which case methionine and cysteine residues are not present. Thus, in these embodiments, X at position 14 can be any hydrophilic amino acid other than methionine or cysteine, preferably S or T.

Exemplary peptides that share the consensus structure with SEQ ID NO: 3, or are derived from SEQ ID NO: 3, are identified in Table 7 below:

TABLE 7 Peptide Variants of Peptide P4 (consensus SEQ ID NO: 3) Name Sequence SEQ ID NO: P4-14S-13D SQGISEKQLDQLDSQLIQALLQP 48 P4-14S-17D SQGISEKQLDQLLSQLDQALLQP 49 P4-14S-21D SQGISEKQLDQLLSQLIQALDQP 50 P4-d18 SQGISEKQLDQLLSQLI_ALLQP 51 P4-14S-9S SQGISEKQSDQLLSQLIQALLQP 52 P4-14S-9Y SQGISEKQYDQLLSQLIQALLQP 53 P4-14S-13Q SQGISEKQLDQLQSQLIQALLQP 54 P4-14S-16S SQGISEKQLDQLLSQSIQALLQP 55 P4-14S-20S SQGISEKQLDQLLSQLIQASLQP 56 P4-14S-9D SQGISEKQDDQLLSQLIQALLQP 58 P4-14S-12D SQGISEKQLDQDLSQLIQALLQP 59 P4-14S-17S SQGISEKQLDQLLSQLSQALLQP 61 P4-14S-16D SQGISEKQLDQLLSQDIQALLQP 161 P4-14S-20D SQGISEKQLDQLLSQLIQADLQP 162 P4-14S-13S SQGISEKQLDQLSSQLIQALLQP 163

In certain other embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of one or more of SEQ ID NOS: 48-56, 58, 59, 61 and 161-163.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Another exemplary family of peptides according to this aspect of the invention have the amino acid sequence of: XXGISEKXJDXJJTXJJXAJJXX  (SEQ ID NO: 4, modified P1 consensus), wherein

-   X at position 1 is N, D, isoD, G, A, or S; -   X at position 2 is Q, E, g-glutamate, G, A, or S; -   X at position 8 is Q, E, g-glutamate, G, A, or S; -   X at position 11 is Q, E, g-glutamate, G, A, or S; -   X at position 15 is Q, E, g-glutamate, G, A, or S; -   X at position 18 is M, T, K, E, g-glutamate, G, A, or S; -   X at position 22 is Q, E, g-glutamate, G, A, or S; -   X at position 23 is Q, E, g-glutamate, G, A, or S; and     J at positions 9, 12, 13, 16, 17, 20, and 21 are hydrophobic amino     acids selected from L, V, I, and F, except that one of the amino     acids at these positions is a non-hydrophobic amino acid or A;     wherein the peptide induces an active plant response, but does not     induce a hypersensitive response, when applied to plant tissue.     Preferably, one to four, not more than three, not more than two, or     exactly one of the residues at positions 9, 12, 13, 16, 17, 20, and     21 is a non-hydrophobic amino acid or A. In one embodiment, not more     than one of the J residues is A, and preferably the A residue is at     one of positions 9, 12, 13, 16, 20, and 21; one or two of the     remaining J residues is optionally a non-hydrophobic amino acid, and     all other J residues are L, I, V, or F. In certain embodiments, not     more than one of the J residues is A, and preferably the A residue     is at one of positions 9, 12, 13, 16, 20, and 21; and all other J     residues are L, I, V, or F.

In certain embodiments, these peptides according to SEQ ID NO: 4 also meet the structural features defining the peptides of SEQ ID NO: 1, in which case methionine and cysteine residues are not present. Thus, in those embodiments, X at position 18 is T, K, E, g-glutamate, G, A, or S.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Exemplary peptides that share the consensus structure with SEQ ID NO: 4 are identified in Table 8 below:

TABLE 8 Peptide Variants of P1 (consensus SEQ ID NO: 4) Peptide Name Sequence SEQ ID NO: P1-13P-20P NQGISEKQLDQLPTQLIMAPLQQ 164 P1 NQGISEKQLDQLLTQLIMALLQQ 165 P1-9D NQGISEKQDDQLLTQLIMALLQQ 166 P1-9S NQGISEKQSDQLLTQLIMALLQQ 167 P1-12D NQGISEKQLDQDLTQLIMALLQQ 168 P1-12S NQGISEKQLDQSLTQLIMALLQQ 169 P1-13D NQGISEKQLDQLDTQLIMALLQQ 170 P1-13S NQGISEKQLDQLSTQLIMALLQQ 171 P1-16D NQGISEKQLDQLLTQDIMALLQQ 172 P1-16S NQGISEKQLDQLLTQSIMALLQQ 173 P1-17D NQGISEKQLDQLLTQLDMALLQQ 174 P1-17S NQGISEKQLDQLLTQLSMALLQQ 175 P1-20D NQGISEKQLDQLLTQLIMADLQQ 176 P1-20S NQGISEKQLDQLLTQLIMASLQQ 177 P1-21D NQGISEKQLDQLLTQLIMALDQQ 178 P1-21S NQGISEKQLDQLLTQLIMALSQQ 179

Additional variants of these peptides may include the substitution of methionine at position 18 with T, K, E, g-glutamate, G, A, or S, as noted above.

In certain other embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of one or more of SEQ ID NOS: 164, 166-179.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Yet another aspect of the invention relates to an isolated peptide having the amino acid sequence of: (i) KPXDSXSXJAKJJSXJJXSJJX  (SEQ ID NO: 5, modified P15b/P20 consensus), wherein

-   -   X at position 3 is N, D, or isoD;     -   X at position 6 is Q, E, g-glutamate, G, A, or S;     -   X at position 8 is N, D, or isoD;     -   X at position 15 is optional and can be any amino acid;     -   X at position 18 is M, E, g-glutamate, G, A, S, T, or K;     -   X at position 22 is optional and can be Q, E, g-glutamate, G, A,         or S; and     -   J at positions 9, 12, 13, 16, 17, 20, and 21 are hydrophobic         amino acids selected from L, V, I, F, and A, except that at         least one of the amino acids at these positions is a         non-hydrophobic amino acid; or         (ii) JAKJJSXJJXSJJX  (SEQ ID NO: 6, modified P15/20 min         consensus), wherein     -   X at position 7 is optional and can be any amino acid;     -   X at position 10 is M, E, g-glutamate, G, A, S, T, or K;     -   X at position 14 is optional and can be Q, E, g-glutamate, G, A,         or S; and     -   J at positions 1, 4, 5, 8, 9, 12, and 13 are hydrophobic amino         acids selected from L, V, I, and F, except that at least one of         the amino acids at these positions is a non-hydrophobic amino         acid or A; and         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue. Preferably, one to four, not more than three, not more         than two, or exactly one of the residues at positions 9, 12, 13,         16, 17, 20, and 21 of SEQ ID NO: 5 is a non-hydrophobic amino         acid or A; and one to four, not more than three, not more than         two, or exactly one of the residues at positions 1, 4, 5, 8, 9,         12, and 13 of SEQ ID NO: 6 is a non-hydrophobic amino acid or A.         In one embodiment, not more than one of the J residues is A, and         preferably the A residue is at one of positions 9, 12, 13, 16,         20, and 21 of SEQ ID NO: 5 or positions 1, 4, 5, 8, 12, and 13         of SEQ ID NO: 6; one or two of the remaining J residues is         optionally a non-hydrophobic amino acid, and all other J         residues are L, I, V, or F. In certain embodiments, not more         than one of the J residues is A, and preferably the A residue is         at one of positions 9, 12, 13, 16, 20, and 21 of SEQ ID NO: 5 or         positions 1, 4, 5, 8, 12, and 13 of SEQ ID NO: 6; and all other         J residues are L, I, V, or F.

Exemplary peptides that share the consensus structure with SEQ ID NO:5 or 6 are identified in Table 9 below:

TABLE 9 Peptide Variants of P15/P20 (consensus SEQ ID NO: 5 or 6) Name Sequence SEQ ID NO: P15b-9D KPNDSQSNDAKLISALIMSLLQ 180 P15b-12D KPNDSQSNIAKDISALIMSLLQ 181 P15b-13D KPNDSQSNIAKLDSALIMSLLQ 182 P15b-16D KPNDSQSNIAKLISADIMSLLQ 183 P15b-17D KPNDSQSNIAKLISALDMSLLQ 184 P15b-20D KPNDSQSNIAKLISALIMSDLQ 185 P15b-21D KPNDSQSNIAKLISALIMSLDQ 186 P15b-9S KPNDSQSNSAKLISALIMSLLQ 187 P15b-12S KPNDSQSNIAKSISALIMSLLQ 188 P15b-13S KPNDSQSNIAKLSSALIMSLLQ 189 P15b-16S KPNDSQSNIAKLISASIMSLLQ 190 P15b-17S KPNDSQSNIAKLISALSMSLLQ 191 P15b-20S KPNDSQSNIAKLISALIMSSLQ 192 P15b-21S KPNDSQSNIAKLISALIMSLSQ 193

Additional variants of these peptides may include the substitution of methionine at position 18 with E, g-glutamate, G, A, S, T, or K, as noted above.

In certain other embodiments, the peptide consists essentially of, or consists of, the amino sequence of one or more of SEQ ID NOS: 180-193.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

A further aspect of the invention relates to an isolated peptide having the amino acid sequence of: PSPJTXJJXXJJGXJJXAXN  (SEQ ID NO: 7, modified P6/6a consensus), wherein

-   -   X at position 6 is Q, E, g-glutamate, G, A, or S;     -   X at position 9 is M, E, g-glutamate, G, A, S, T, or K;     -   X at position 10 is H or N;     -   X at position 14 is E, g-glutamate, D, or isoD;     -   X at position 17 is Q, E, g-glutamate, G, A, or S;     -   X at position 19 is Q, E, g-glutamate, G, A, or S; and     -   J at positions 4, 7, 8, 11, 12, 15, and 16 are hydrophobic amino         acids selected from L, V, I, M, and F, except that at least one         of the amino acids at these positions in a non-hydrophobic amino         acid or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue. Preferably, one to four, not more than three, not more         than two, or exactly one of the residues at positions 4, 7, 8,         11, 12, 15, and 16 is a non-hydrophobic amino acid or A. In one         embodiment, not more than one of the J residues is A, and         preferably the A residue is at one of positions 4, 7, 8, 11, 15,         and 16 of SEQ ID NO: 7; one or two of the remaining J residues         is optionally a non-hydrophobic amino acid, and all other J         residues are L, I, V, M, or F. In certain embodiments, not more         than one of the J residues is A, and preferably the A residue is         at one of positions 4, 7, 8, 11, 15, and 16 of SEQ ID NO: 7; and         all other J residues are L, I, V, M, or F.

Exemplary peptides that share the consensus structure with SEQ ID NO: 7 are identified in Table 10 below:

TABLE 10 Peptide Variants of P6/6a (consensus SEQ ID NO: 7) Name Sequence SEQ ID NO: P6a-4D PSPDTQMLMHIVGEILQAQN 194 P6a-7D PSPFTQDLMHIVGEILQAQN 195 P6a-8D PSPFTQMDMHIVGEILQAQN 196 P6a-11D PSPFTQMLMHDVGEILQAQN 197 P6a-12D PSPFTQMLMHIDGEILQAQN 198 P6a-15D PSPFTQMLMHIVGEDLQAQN 199 P6a-16D PSPFTQMLMHIVGEIDQAQN 200 P6a-4S PSPSTQMLMHIVGEILQAQN 201 P6a-7S PSPFTQSLMHIVGEILQAQN 202 P6a-8S PSPFTQMSMHIVGEILQAQN 203 P6a-11S PSPFTQMLMHSVGEILQAQN 204 P6a-12S PSPFTQMLMHISGEILQAQN 205 P6a-15S PSPFTQMLMHIVGESLQAQN 206 P6a-16S PSPFTQMLMHIVGEISQAQN 207

Additional variants of these peptides may include the substitution of methionine at position 7 with L, I, V, F, a non-hydrophobic amino acid, or A, as noted above; and substitution of methionine at position 9 with L, E, g-glutamate, G, A, S, T, or K, as noted above.

In certain other embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of one or more of SEQ ID NOS: 194-207.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Another aspect of the invention relates to a peptide having the amino acid sequence of: (i) XXXXXXJXXJJXXJJXJJK  (SEQ ID NO: 8, modified P14d consensus), wherein

-   -   X at position 1 can be: Q, N, D, E, g-glutamate, isoD, or S;     -   X at position 2 can be: D, E, g-glutamate, isoD;     -   X at position 3 can be: P, D, E, isoD, or g-glutamate;     -   X at position 4 can be M, A, S, D, E, isoD, or g-glutamate     -   X at position 5 can be Q, E, or g-glutamate;     -   X at position 6 can be A, E, or g-glutamate;     -   X at position 8 can be M, L, E, Q, D, N, G, A, S, isoD, or         g-glutamate;     -   X at position 9 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 12 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 13 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 16 can be K, Q, N, E, D, R, G, A, or S; and         J at positions 7, 10, 11, 14, 15, 17, and 18 are hydrophobic         amino acids selected from L, V, I, and F, except that at least         one of the amino acids at these positions is a non-hydrophobic         amino acid or A; or         (ii) JXXJJXXJJXJJK  (SEQ ID NO: 9, modified P14d min consensus),         wherein     -   X at position 2 can be M, L, E, Q, D, N, G, A, S, isoD, or         g-glutamate;     -   X at position 3 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 6 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 7 can be Q, N, E, D, G, A, S, isoD, or         g-glutamate;     -   X at position 10 can be K, Q, N, E, D, R, G, A, or S; and         J at positions 1, 4, 5, 8, 9, 11, and 12 are hydrophobic amino         acids selected from L, V, I, and F, except that at least one of         the amino acids at these positions is a non-hydrophobic amino         acid or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue. Preferably, one to four, not more than three, not more         than two, or exactly one of the residues at positions 7, 10, 11,         14, 15, 17, and 18 of SEQ ID NO: 8 is a non-hydrophobic amino         acid or A; and one to four, not more than three, not more than         two, or exactly one of the residues at positions 1, 4, 5, 8, 9,         11, and 12 of SEQ ID NO: 9 is a non-hydrophobic amino acid or A.         In one embodiment, not more than one of the J residues is A, and         preferably the A residue is at one of positions 7, 10, 11, 14,         17, and 18 of SEQ ID NO: 8 or positions 1, 4, 5, 8, 11, and 12         of SEQ ID NO: 9; one or two of the remaining J residues is         optionally a non-hydrophobic amino acid, and all other J         residues are L, I, V, or F. In certain embodiments, not more         than one of the J residues is A, and preferably the A residue is         at one of positions 7, 10, 11, 14, 17, and 18 of SEQ ID NO: 8 or         positions 1, 4, 5, 8, 11, and 12 of SEQ ID NO: 9; and all other         J residues are L, I, V, or F.

Exemplary peptides that share the consensus structure with SEQ ID NO: 8 or 9 are identified in Table 11 below:

TABLE 11 Peptide Variants of P14d (consensus SEQ ID NO: 8 or 9) Name Sequence SEQ ID NO: P14d-7D QDPMQADMQLLEDLVKLLK 208 P14d-10D QDPMQALMQDLEDLVKLLK 209 P14d-11D QDPMQALMQLDEDLVKLLK 210 P14d-14D QDPMQALMQLLEDDVKLLK 211 P14d-15D QDPMQALMQLLEDLDKLLK 212 P14d-17D QDPMQALMQLLEDLVKDLK 213 P14d-18D QDPMQALMQLLEDLVKLDK 214 P14d-7S QDPMQASMQLLEDLVKLLK 215 P14d-10S QDPMQALMQSLEDLVKLLK 216 P14d-11S QDPMQALMQLSEDLVKLLK 217 P14d-14S QDPMQALMQLLEDSVKLLK 218 P14d-15S QDPMQALMQLLEDLSKLLK 219 P14d-17S QDPMQALMQLLEDLVKSLK 220 P14d-18S QDPMQALMQLLEDLVKLSK 221

Additional variants of these peptides may include the substitution of methionine at one or both of positions 4 and 8 with L, E, Q, D, N, G, A, S, isoD, or g-glutamate, as noted above.

In certain other embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of one or more of SEQ ID NOS: 208-221.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

A further aspect of the invention relates to a peptide having the amino acid sequence of: (i) JXXJJXJJXXJJ  (SEQ ID NO: 10, modified P25 consensus) wherein

-   -   X at position 2 can be Q, N, E, g-glutamate, D, isoD, T, S, A,         or G;     -   X at position 3 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 6 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 9 can be E, g-glutamate, D, isoD, Q, N, T, S, A,         or G;     -   X at position 10 can be A, G, S, T, E, g-glutamate, D, isoD, Q,         or N; and     -   J at positions 1, 4, 5, 7, 8, 10, and 11 are hydrophobic amino         acids selected from L, V, I, F, and M, except that at least one         of the amino acids at these positions is a non-hydrophobic amino         acid or A; or         (ii) JXXJJXXJJXJJXXJJ  (SEQ ID NO: 11, modified P25 consensus)         wherein     -   X at position 2 can be T, S, A, G, D, isoD, E, g-glutamate, Q,         or N;     -   X at position 3 can be G, T, S, A, D, isoD, E, g-glutamate, Q,         or N;     -   X at position 6 can be Q, N, E, g-glutamate, D, isoD, T, S, A,         or G;     -   X at position 7 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 10 can be K, Q, N, E, g-glutamate, D, isoD, T, S,         A, or G;     -   X at position 13 can be E, g-glutamate, D, isoD, Q, N, T, S, A,         or G;     -   X at position 14 can be A, G, S, T, E, g-glutamate, D, isoD, Q,         or N;     -   J at positions 1, 4, 5, 8, 9, 11, 12, and 15 are hydrophobic         amino acids selected from L, V, I, F, and M, except that at         least one of the amino acids at these positions is a         non-hydrophobic amino acid or A; and     -   J at position 16 is optional and a hydrophobic amino acid         selected from L, V, I, and F;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue. Preferably, one to four, not more than three, not more         than two, or exactly one of the residues at positions 1, 4, 5,         7, 8, 10, and 11 of SEQ ID NO: 10 is a non-hydrophobic amino         acid, and one to four, not more than three, not more than two,         or exactly one of the residues at positions 1, 4, 5, 8, 9, 11,         12, 15, and 16 of SEQ ID NO: 11 is a non-hydrophobic amino acid.         In one embodiment, not more than one of the J residues is A, and         preferably the A residue is at one of positions 1, 4, 5, 7, 10,         and 11 of SEQ ID NO: 10 or positions 1, 4, 5, 8, 11, 12, 15, and         16 of SEQ ID NO: 11; one or two of the remaining J residues is         optionally a non-hydrophobic amino acid, and all other J         residues are L, I, V, or F. In certain embodiments, not more         than one of the J residues is A, and preferably the A residue is         at one of positions 1, 4, 5, 7, 10, and 11 of SEQ ID NO: 10 or         positions 1, 4, 5, 8, 11, 12, 15, and 16 of SEQ ID NO: 11; and         all other J residues are L, I, V, or F.

Exemplary peptides that share the consensus structure with SEQ ID NO: 10 or 11 are identified in Table 12 below:

TABLE 12 Peptide Variants of P25 (consensus SEQ ID NO: 10 or 11) Name Sequence SEQ ID NO: P25-5D GGLTDTGVLQKLMKILNALVQ 222 P25-8D GGLTLTGDLQKLMKILNALVQ 223 P25-9D GGLTLTGVDQKLMKILNALVQ 224 P25-12D GGLTLTGVLQKDMKILNALVQ 225 P25-13D GGLTLTGVLQKLDKILNALVQ 226 P25-15D GGLTLTGVLQKLMKDLNALVQ 227 P25-16D GGLTLTGVLQKLMKIDNALVQ 228 P25-19D GGLTLTGVLQKLMKILNADVQ 229 P25-20D GGLTLTGVLQKLMKILNALDQ 230 P25-5S GGLTSTGVLQKLMKILNALVQ 231 P25-8S GGLTLTGSLQKLMKILNALVQ 232 P25-9S GGLTLTGVSQKLMKILNALVQ 233 P25-12S GGLTLTGVLQKSMKILNALVQ 234 P25-13S GGLTLTGVLQKLSKILNALVQ 235 P25-15S GGLTLTGVLQKLMKSLNALVQ 236 P25-16S GGLTLTGVLQKLMKISNALVQ 237 P25-19S GGLTLTGVLQKLMKILNASVQ 238 P25-20S GGLTLTGVLQKLMKILNALSQ 239

Additional variants of these peptides may include the substitution of methionine at position 13 with L, V, I, and F, as noted above.

In certain other embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of one or more of SEQ ID NOS: 222-239.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Still another aspect of the invention relates to a peptide having the amino acid sequence: (i) XXXXXXXXXXXJXXJJXXJJXXJJXXX  (SEQ ID NO: 12, modified P17/18), wherein

-   -   X at position 1 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 2 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 3 can be any amino acid, but preferably P, Q, S,         E, g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 4 can be any amino acid, but preferably I, Q, S,         E, g-glutamate, A, T, G, D, N, isoD, K, or R;     -   X at position 5 can be any amino acid, but preferably D, isoD,         S, E, g-glutamate, A, T, G, N, Q, K, or R;     -   X at position 6 can be any amino acid, but preferably R, Q, S,         E, g-glutamate, A, T, G, D, isoD, N, or K;     -   X of position 7 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 8 can be any amino acid, but preferably T, Q, S,         E, g-glutamate, A, G, D, isoD, N, K, or R;     -   X at position 9 can be any amino acid, but preferably I, Q, S,         E, g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 10 can be any amino acid, but preferably E,         g-glutamate, Q, S, A, T, G, D, isoD, N, K, or R;     -   X at position 11 can be any amino acid, but preferably Q, S, E,         g-glutamate, A, T, G, D, isoD, N, K, or R;     -   X at position 13 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 14 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 17 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 18 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 21 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 22 can be any amino acid, but preferably S, A, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 25 can be any amino acid, but preferably S, A, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 26 can be any amino acid, but preferably P, S, A,         T, G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 27 can be any amino acid, but preferably Q, S, A,         T, G, D, isoD, E, g-glutamate, N, K, or R; and     -   J at positions 12, 15, 16, 19, 20, 23, and 24 are hydrophobic         amino acids selected from L, V, I, F, and M, except that at         least one of the amino acids at these positions is a         non-hydrophobic amino acid or A;     -   or         (ii) JXXJJXXJJXXJJ  (SEQ ID NO: 13, modified P17/18 min         consensus), wherein     -   X at position 2 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 3 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 6 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 7 can be any amino acid, but preferably Q, A, S,         T, G, D, isoD, E, g-glutamate, N, K, or R;     -   X at position 10 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 11 can be any amino acid, but preferably S, A, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R; and     -   J at positions 1, 4, 5, 8, 9, 12, and 13 are hydrophobic amino         acids selected from L, V, I, F, and M, except that at least one         of the amino acids at these positions is a non-hydrophobic amino         acid or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue. Preferably, one to four, not more than three, not more         than two, or exactly one of the residues at positions 12, 15,         16, 19, 20, 23, and 24 of SEQ ID NO: 12 is a non-hydrophobic         amino acid or A; and one to four, not more than three, not more         than two, or exactly one of the residues at positions 1, 4, 5,         8, 9, 12, and 13 of SEQ ID NO: 13 is a non-hydrophobic amino         acid or A. In one embodiment, not more than one of the J         residues is A, and preferably the A residue is at one of         positions 12, 15, 16, 19, 23, and 24 of SEQ ID NO: 12 or         positions 1, 4, 5, 8, 12, and 13 of SEQ ID NO: 13; one or two of         the remaining J residues is optionally a non-hydrophobic amino         acid, and all other J residues are L, I, V, F, or M. In certain         embodiments, not more than one of the J residues is A, and         preferably the A residue is at one of positions 12, 15, 16, 19,         23, and 24 of SEQ ID NO: 12 or positions 1, 4, 5, 8, 12, and 13         of SEQ ID NO: 13; and all other J residues are L, I, V, F, or M.

Exemplary peptides that share the consensus structure with SEQ ID NO: 12 or 13, or are derived from SEQ ID NO: 12 or 13 and meet the consensus structure of SEQ ID NO: 1, are identified in Table 13 below:

TABLE 13 Peptide Variants of P17/P18 (consensus SEQ ID NO: 12 or 13) Name Sequence SEQ ID NO: P18min-7D SEEEEE DAQLLAQLLKSLL 85 P18min-10D SEEEEELAQDLAQLLKSLL 86 P18min-11D SEEEEELAQLDAQLLKSLL 87 P18min-14D SEEEEELAQLLAQDLKSLL 88 P18min-15D SEEEEELAQLLAQLDKSLL 89 P18min-18D SEEEEELAQLLAQLLKSDL 90 P18min-19D SEEEEELAQLLAQLLKSLD 91 P18min-7S SEEEEE SAQLLAQLLKSLL 92 P18min-10S SEEEEELAQSLAQLLKSLL 93 P18min-11S SEEEEELAQLSAQLLKSLL 94 P18min-14S SEEEEELAQLLAQSLKSLL 95 P18min-15S SEEEEELAQLLAQLSKSLL 96 P18min-18S SEEEEELAQLLAQLLKSSL 97 P18min-19S SEEEEELAQLLAQLLKSLS 98 In Table 13, peptides include the solubility tag SEEEEE, indicated by italic print. Peptides comprising the sequences shown in Table 13 but lacking this specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain other embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of one or more of SEQ ID NOS: 85-98.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Yet another aspect of the invention relates to a peptide having the amino acid sequence: XJXXJJXJJXXJJ  (SEQ ID NO: 14, modified P19 consensus), wherein

-   -   X at position 1 is optional and can be L, I, V, F, or M;     -   X at position 3 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 4 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 7 can be any amino acid, but preferably K, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 10 can be any amino acid, but preferably A, S, T,         G, D, isoD, E, g-glutamate, Q, N, K, or R;     -   X at position 11 can be any amino acid, but preferably R, A, S,         T, G, D, isoD, E, g-glutamate, Q, N, or K; and     -   J at positions 2, 5, 6, 8, 9, 12, and 13 are hydrophobic amino         acids selected from L, V, I, F, and M, except that at least one         of the amino acids at these positions is a non-hydrophobic amino         acid or A;         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue. Preferably, one to four, not more than three, not more         than two, or exactly one of the residues at positions 2, 5, 6,         8, 9, 12, and 13 is a non-hydrophobic amino acid. In one         embodiment, not more than one of the J residues is A, and         preferably the A residue is at one of positions 2, 5, 6, 8, 12,         and 13 of SEQ ID NO: 14; one or two of the remaining J residues         is optionally a non-hydrophobic amino acid, and all other J         residues are L, I, V, F, or M. In certain embodiments, not more         than one of the J residues is A, and preferably the A residue is         at one of positions 2, 5, 6, 8, 12, and 13 of SEQ ID NO: 14; and         all other J residues are L, I, V, F, or M.

Exemplary peptides that share the consensus structure with one of SEQ ID NO: 14, or are derived from one of SEQ ID NO: 14 and meet the consensus structure of SEQ ID NO: 1, are identified in Table 14 below:

TABLE 14 Peptide Variants of P19 (consensus SEQ ID NO: 14) Name Sequence SEQ ID NO: P19min-7D SEEEEE DKALLKLIARLL 99 P19min-10D SEEEEELKADLKLIARLL 100 P19min-11D SEEEEELKALDKLIARLL 101 P19min-13D SEEEEELKALLKDIARLL 102 P19min-14D SEEEEELKALLKLDARLL 103 P19min-17D SEEEEELKALLKLIARDL 104 P19min-18D SEEEEELKALLKLIARLD 105 P19min-7S SEEEEE SKALLKLIARLL 106 P19min-10S SEEEEELKASLKLIARLL 107 P19min-11S SEEEEELKALSKLIARLL 108 P19min-13S SEEEEELKALLKSIARLL 109 P19min-14S SEEEEELKALLKLSARLL 110 P19min-17S SEEEEELKALLKLIARSL 111 P19min-18S SEEEEELKALLKLIARLS 112 In Table 14, peptides include the solubility tag SEEEEE, indicated by italic print. Peptides comprising the sequences shown in Table 14 but lacking this specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of SEQ ID NOS: 99-112.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

A further aspect of the invention relates to an isolated peptide that includes the amino acid sequence of: Z₁-LLXLFXXIL-Z₂  (SEQ ID NO: 126, P3 minimum) wherein

-   -   X at position 3 is any hydrophilic amino acid, preferably K, A,         S, T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 6 is any hydrophilic amino acid, preferably K, A,         S, T, G, D, isoD, E, g-glutamate, Q, N, or R;     -   X at position 7 is any hydrophilic amino acid, preferably K, A,         S, T, G, D, isoD, E, g-glutamate, Q, N, or R; and     -   wherein one of Z₁ and Z₂ is present, but preferably not both,         with Z₁ comprising LXX- where each X is a hydrophilic amino         acid, preferably K, A, S, T, G, D, isoD, E, g-glutamate, Q, N,         or R, and with Z₂ comprising -XXLF where each X is a hydrophilic         amino acid, preferably K, A, S, T, G, D, isoD, E, g-glutamate,         Q, N, or R.         wherein the peptide induces an active plant response, but does         not induce a hypersensitive response, when applied to plant         tissue.

In one embodiment, Z₁ but not Z₂ is present. In an alternative embodiment, Z₂ but not Z₁ is present.

Exemplary peptides that share the consensus structure with SEQ ID NO: 126, or are derived from SEQ ID NO: 126 and meet the consensus structure of SEQ ID NO: 1, are identified in Table 15 below:

TABLE 15 Peptide Variants of P3 (consensus SEQ ID NO: 126) Name Sequence SEQ ID NO: P3-5 SEEELQQLLKLFSEIL 156 P3-8 SEEEEEELLKLFSEILQSLF 157 P3-9 SEEEEQQLLKLFSEILQSLF 158 P3-10 SEEEEELQQLLKLFSEILQ 159 In Table 15, peptides include the solubility tag SEEE, SEEEE, and SEEEEEE, indicated by italic print. Peptides comprising the sequences shown in Table 15 but lacking this specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of SEQ ID NOS: 156-159.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

Another aspect of the invention relates to an isolated peptide that includes the amino acid sequence of: L-X-X-(L/I)-(L/I)-X-X-(L/I/V)-(L/I/V)  (SEQ ID NO: 116) wherein the peptide is free of cysteine and methionine; each X at positions 2, 3, 6, 7 is any amino acid; and the peptide induces an active plant response, but does not induce a hypersensitive response, when applied to plant tissue.

In certain embodiments, X at one or more of positions 2, 3, 6, and 7 is a non-hydrophobic amino acid, X at two or more of positions 2, 3, 6, and 7 is a non-hydrophobic amino acid, X at three or more of positions 2, 3, 6, and 7 is a non-hydrophobic amino acid, or X at each of positions 2, 3, 6, and 7 is a non-hydrophobic amino acid. In this embodiment, the non-hydrophobic amino acids independently may be any one of G, A, S, T, D, isoD, E, g-glutamate, Q, N, K, and R.

The peptides according to this aspect of the invention are generally denoted by a truncation of the HR box sequence, which is described in co-pending U.S. patent application Ser. No. 14/872,298, entitled “Hypersensitive Response Elicitor Peptides and Use Thereof”, filed Oct. 1, 2015, which is hereby incorporated by reference in its entirety. Thus, by virtue of the truncation of the HR box sequence, either by termination of the peptide or substitution of amino acid residues that form part of the HR box sequence, the isolated peptide according to this aspect do not comprise the amino acid sequence: (L/I/V/F)-X-X-(L/I/V/F)-(L/I)-X-X-(L/I/V)-(L/I)-X-X-(L/I/V/F)-(L/I/V/F)  (SEQ ID NO: 125) wherein each X at positions 2, 3, 6, 7, 10, 11 is any amino acid.

Exemplary peptides that share the consensus structure with SEQ ID NO: 116 are identified in Table 16 below:

TABLE 16 SEQ ID Name Sequence NO: P14-22L, 26L QAGPQSANKTGNVDDANNQDPLQALLQLLEDLV 115 P14-32 SEEEEELEQLLEDLVKLL 124 P14-31 SEEEEEALEQLLEDLVKLL 129 P14-39 SEEEEELEQLLEDLV 160 P14-41 SEEEEELLQLLEDLV 128 P1-29 NQGISEKQLDQLLTQLI 130 P1-31 SEEEELDQLLTQLI 131 P4-111 SQGISEKQLDQLLSQLI 132 P4-115 SEEEELDQLLSQLI 139 P18-9 SEEEEE LAQLLAQLL 143 P19-12 SEEEEEKALLKLIARLL 146 P19-13 SEEEEEALLKLIARLL 147 P15-61 SEEEEEEEIAKLIS_LIESLL 151 P25-9 SEEEEELQKLLK_ILEALV 152 In Table 16, peptides include the solubility tags SEEEE and SEEEEE, indicated by italic print. Peptides comprising the sequences shown in Table 15 but lacking the specific solubility tag (or having a different solubility tag) are also contemplated herein.

In certain embodiments, the isolated peptide consists essentially of, or consists of, the amino acid sequence of SEQ ID NOS: 115, 124, 128-132, 139, 143, 146, 147, 151, 152, and 160.

In this embodiment, the isolated peptide is preferably stable when dissolved in water; resistant to chemical degradation in aqueous conditions in the presence of a pH buffer and a biocide, as described above; and/or has a solubility in an aqueous solution of at least about 1.0 mg/ml.

The isolated peptides of the invention can also be presented in the form of a fusion peptide that includes, in addition, a second amino acid sequence coupled to the inventive peptides via peptide bond. The second amino acid sequence can be a purification tag, such as poly-histidine (His₆−), a glutathione-S-transferase (GST−), or maltose-binding protein (MBP−), which assists in the purification but can later be removed, i.e., cleaved from the peptide following recovery. Protease-specific cleavage sites or chemical-specific cleavage sites (i.e., in a cleavable linker sequence) can be introduced between the purification tag and the desired peptide. Protease-specific cleavage sites are well known in the literature and include, without limitation, the enterokinase specific cleavage site (Asp)₄-Lys, which is cleaved after lysine; the factor Xa specific cleavage site Ile-(Glu or Asp)-Gly-Arg, which is cleaved after arginine; the trypsin specific cleavage site, which cleaves after Lys and Arg; and the Genenase™ I specific cleavage site Pro-Gly-Ala-Ala-His-Tyr. Chemicals and their specific cleavage sites include, without limitation, cyanogen bromide (CNBr), which cleaves at methionine (Met) residues; BNPS-skatole, which cleaves at tryptophan (Trp) residues; formic acid, which cleaves at aspartic acid-proline (Asp-Pro) peptide bonds; hydroxylamine, which cleaves at asparagine-glycine (Asn-Gly) peptide bonds; and 2-nitro-5-thiocyanobenzoic acid (NTCB), which cleaves at cysteine (Cys) residues (see Crimmins et al., “Chemical Cleavage of Proteins in Solution,” Curr. Protocol. Protein Sci., Chapter 11:Unit 11.4 (2005), which is hereby incorporated by reference in its entirety). In order to use one of these cleavage methods, it may be necessary to remove unwanted cleavage sites from within the desired peptide sequences by mutation. For example, P14-22E,26E-R (SEQ ID NO: 23) has been mutated for compatibility with trypsin: the lysine residue at position 9 is mutated to a glutamate and a C-terminal arginine is added to represent the product of a theoretical trypsin cleavage. The desired peptide product can be purified further to remove the cleaved purification tags.

The isolated peptides of the invention can also be presented in the form of a fusion peptide that includes multiple peptide sequences of the present invention linked together by a linker sequence, which may or may not take the form of a cleavable amino acid sequence of the type described above. Such multimeric fusion proteins may or may not include purification tags. In one embodiment, each monomeric sequence can include a purification tag linked to a peptide of the invention by a first cleavable peptide sequence; and the several monomeric sequences can be linked to adjacent monomeric sequences by a second cleavable peptide sequence. Consequently, upon expression of the multimeric fusion protein, i.e., in a host cell, the recovered fusion protein can be treated with a protease or chemical that is effective to cleave the second cleavable peptide sequence, thereby releasing individual monomeric peptide sequences containing purification tags. Upon affinity purification, the recovered monomeric peptide sequences can be treated with a protease or chemical that is effective to cleave the first cleavable peptide sequence and thereby release the purification tag from the peptide of interest. The latter can be further purified using gel filtration and/or HPLC as described infra.

These fusion proteins may include the sequences, identified above as SEQ ID NO: 15-18, which were previously identified in Haapalainen et al., “Functional Mapping of Harpin HrpZ of Pseudomonas syringae Reveals the Sites Responsible for Protein Oligomerization, Lipid Interactions, and Plant Defence Induction,” Mol. Plant Pathol. 12(2):151-66 (2011), which is hereby incorporated by reference in its entirety.

According to one approach, the peptides of the present invention can be synthesized by standard peptide synthesis operations. These include both FMOC (9-fluorenylmethyloxy-carbonyl) and tBoc (tert-butyloxy-carbonyl) synthesis protocols that can be carried out on automated solid phase peptide synthesis instruments including, without limitation, the Applied Biosystems 431 A, 433 A synthesizers and Peptide Technologies Symphony or large scale Sonata or CEM Liberty automated solid phase peptide synthesizers. The use of alternative peptide synthesis instruments is also contemplated. Peptides prepared using solid phase synthesis are recovered in a substantially pure form.

The peptides of the present invention may be also prepared by using recombinant expression systems followed by separation and purification of the recombinantly prepared peptides. Generally, this involves inserting an encoding nucleic acid molecule into an expression system to which the molecule is heterologous (i.e., not normally present). One or more desired nucleic acid molecules encoding a peptide of the invention may be inserted into the vector. The heterologous nucleic acid molecule is inserted into the expression system or vector in proper sense (5′-3′) orientation and correct reading frame relative to the promoter and any other 5′ and 3′ regulatory molecules. Representative nucleotide sequences for expression in bacteria and plant hosts and included in Table 17 below:

TABLE 17 Peptide & SEQ Optimized ID Host Nucleotide Sequence NO: P14 CAAGCTGGACCTCAATCTGCTAATAAGACTGGA 240 A. thaliana AATGTTGATGATGCTAATAATCAAGATCCTATG CAAGCTCTTATGCAACTTCTTGAAGATCTTGTT P14 CAGGCAGGTCCGCAGAGCGCAAATAAAACCGGT 241 E. coli AATGTTGATGATGCAAATAATCAGGATCCGATG CAGGCACTGATGCAGCTGCTGGAAGATCTGGTT P14d-10D CAAGATCCTATGCAAGCTCTTATGCAAGATCTT 242 A. thaliana GAAGATCTTGTTAAGCTTCTTAAG P14d-10D CAGGATCCGATGCAGGCACTGATGCAGGATCTG 243 E. coli GAAGATCTGGTTAAACTGCTGAAA

With knowledge of the encoded amino acid sequence listed herein and the desired transgenic organism, additional codon-optimized DNA sequences and RNA sequences can be generated with nothing more than routine skill.

Expression (including transcription and translation) of a peptide or fusion polypeptide of the invention by the DNA construct may be regulated with respect to the level of expression, the tissue type(s) where expression takes place and/or developmental stage of expression. A number of heterologous regulatory sequences (e.g., promoters and enhancers) are available for controlling the expression of the DNA construct. These include constitutive, inducible and regulatable promoters, as well as promoters and enhancers that control expression in a tissue- or temporal-specific manner. Exemplary constitutive promoters include the raspberry E4 promoter (U.S. Pat. Nos. 5,783,393 and 5,783,394, each of which is hereby incorporated by reference in its entirety), the nopaline synthase (NOS) promoter (Ebert et al., Proc. Natl. Acad. Sci. (U.S.A.) 84:5745-5749 (1987), which is hereby incorporated by reference in its entirety), the octopine synthase (OCS) promoter (which is carried on tumor-inducing plasmids of Agrobacterium tumefaciens), the caulimovirus promoters such as the cauliflower mosaic virus (CaMV) 19S promoter (Lawton et al., Plant Mol. Biol. 9:315-324 (1987), which is hereby incorporated by reference in its entirety) and the CaMV 35S promoter (Odell et al., Nature 313:810-812 (1985), which is hereby incorporated by reference in its entirety), the figwort mosaic virus 35S-promoter (U.S. Pat. No. 5,378,619, which is hereby incorporated by reference in its entirety), the light-inducible promoter from the small subunit of ribulose-1,5-bis-phosphate carboxylase (ssRUBISCO), the Adh promoter (Walker et al., Proc. Natl. Acad. Sci. (U.S.A.) 84:6624-6628 (1987), which is hereby incorporated by reference in its entirety), the sucrose synthase promoter (Yang et al., Proc. Natl. Acad. Sci. (U.S.A.) 87:4144-4148 (1990), which is hereby incorporated by reference in its entirety), the R gene complex promoter (Chandler et al., Plant Cell 1:1175-1183 (1989), which is hereby incorporated by reference in its entirety), the chlorophyll a/b binding protein gene promoter, the CsVMV promoter (Verdaguer et al., Plant Mol Biol., 37:1055-1067 (1998), which is hereby incorporated by reference in its entirety), and the melon actin promoter (PCT Publ. No. WO00/56863, which is hereby incorporated by reference in its entirety). Exemplary tissue-specific promoters include the tomato E4 and E8 promoters (U.S. Pat. No. 5,859,330, which is hereby incorporated by reference in its entirety) and the tomato 2AII gene promoter (Van Haaren et al., Plant Mol Bio., 21:625-640 (1993), which is hereby incorporated by reference in its entirety).

In one preferred embodiment, expression of the DNA construct is under control of regulatory sequences from genes whose expression is associated with early seed and/or embryo development. Indeed, in a preferred embodiment, the promoter used is a seed-enhanced promoter. Examples of such promoters include the 5′ regulatory regions from such genes as napin (Kridl et al., Seed Sci. Res. 1:209:219 (1991), which is hereby incorporated by reference in its entirety), globulin (Belanger and Kriz, Genet. 129: 863-872 (1991), GenBank Accession No. L22295, each of which is hereby incorporated by reference in its entirety), gamma zein Z 27 (Lopes et al., Mol Gen Genet. 247:603-613 (1995), which is hereby incorporated by reference in its entirety), L3 oleosin promoter (U.S. Pat. No. 6,433,252, which is hereby incorporated by reference in its entirety), phaseolin (Bustos et al., Plant Cell 1(9):839-853 (1989), which is hereby incorporated by reference in its entirety), arcelin5 (U.S. Application Publ. No. 2003/0046727, which is hereby incorporated by reference in its entirety), a soybean 7S promoter, a 7Sa promoter (U.S. Application Publ. No. 2003/0093828, which is hereby incorporated by reference in its entirety), the soybean 7Sαβ conglycinin promoter, a 7Sα promoter (Beachy et al., EMBO J. 4:3047 (1985); Schuler et al., Nucleic Acid Res. 10(24):8225-8244 (1982), each of which is hereby incorporated by reference in its entirety), soybean trypsin inhibitor (Riggs et al., Plant Cell 1(6):609-621 (1989), which is hereby incorporated by reference in its entirety), ACP (Baerson et al., Plant Mol. Biol., 22(2):255-267 (1993), which is hereby incorporated by reference in its entirety), stearoyl-ACP desaturase (Slocombe et al., Plant Physiol. 104(4):167-176 (1994), which is hereby incorporated by reference in its entirety), soybean a′ subunit of β-conglycinin (Chen et al., Proc. Natl. Acad. Sci. 83:8560-8564 (1986), which is hereby incorporated by reference in its entirety), Vicia faba USP (U.S. Application Publ. No. 2003/229918, which is hereby incorporated by reference in its entirety) and Zea mays L3 oleosin promoter (Hong et al., Plant Mol. Biol., 34(3):549-555 (1997), which is hereby incorporated by reference in its entirety).

Nucleic acid molecules encoding the peptides of the present invention can be prepared via solid-phase synthesis using, e.g., the phosphoramidite method and phosphoramidite building blocks derived from protected 2′-deoxynucleosides. To obtain the desired oligonucleotide, the building blocks are sequentially coupled to the growing oligonucleotide chain in the order required by the sequence of the product. Upon the completion of the chain assembly, the product is released from the solid phase to solution, deprotected, collected, and typically purified using HPLC. The limits of solid phase synthesis are suitable for preparing oligonucleotides up to about 200 nt in length, which encodes peptides on the order of about 65 amino acids or less. The ends of the synthetized oligonucleotide can be designed to include specific restriction enzyme cleavage site to facilitate ligation of the synthesized oligonucleotide into an expression vector.

For longer peptides, oligonucleotides can be prepared via solid phase synthesis and then the synthetic oligonucleotide sequences ligated together using various techniques. Recombinant techniques for the fabrication of whole synthetic genes are reviewed, for example, in Hughes et al., “Chapter Twelve—Gene Synthesis: Methods and Applications,” Methods in Enzymology 498:277-309 (2011), which is hereby incorporated by reference in its entirety.

Once a suitable expression vector is selected, the desired nucleic acid sequences are cloned into the vector using standard cloning procedures in the art, as described by Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Springs Laboratory, Cold Springs Harbor, N.Y. (1989), or U.S. Pat. No. 4,237,224 to Cohen and Boyer, which are hereby incorporated by reference in their entirety. The vector is then introduced to a suitable host.

A variety of host-vector systems may be utilized to recombinantly express the peptides of the present invention. Primarily, the vector system must be compatible with the host used. Host-vector systems include, without limitation, the following: bacteria transformed with bacteriophage DNA, plasmid DNA, or cosmid DNA; microorganisms such as yeast containing yeast vectors; mammalian cell systems infected with virus (e.g., vaccinia virus, adenovirus, etc.); insect cell systems infected with virus (e.g., baculovirus); and plant cells infected by Agrobacterium. The expression elements of these vectors vary in their strength and specificities. Depending upon the host-vector system utilized, any one of a number of suitable transcription and translation elements can be used to carry out this and other aspects of the present invention.

Purified peptides may be obtained by several methods. The peptide is preferably produced in purified form (preferably at least about 80% or 85% pure, more preferably at least about 90% or 95% pure) by conventional techniques. Depending on whether the recombinant host cell is made to secrete the peptide into growth medium (see U.S. Pat. No. 6,596,509 to Bauer et al., which is hereby incorporated by reference in its entirety), the peptide can be isolated and purified by centrifugation (to separate cellular components from supernatant containing the secreted peptide) followed by sequential ammonium sulfate precipitation of the supernatant. The fraction containing the peptide is subjected to gel filtration in an appropriately sized dextran or polyacrylamide column to separate the peptides from other proteins. If necessary, the peptide fraction may be further purified by HPLC.

Alternatively, if the peptide of interest of interest is not secreted, it can be isolated from the recombinant cells using standard isolation and purification schemes. This includes disrupting the cells (e.g., by sonication, freezing, French press, etc.) and then recovering the peptide from the cellular debris. Purification can be achieved using the centrifugation, precipitation, and purification procedures described above. The use of purification tags, described above, can simplify this process.

In certain embodiments, purification is not required. Where purification is not performed, cell-free lysates can be recovered following centrifugation for removal of cellular debris. The resulting cell-free lysate can be treated with heat for a sufficient amount of time to deactivate any native proteases in the recovered fraction, e.g., 10 min at 100° C. If desired, one or more of biocidal agents, protease inhibitors, and non-ionic surfactants can be introduced to such a cell-free preparation (see U.S. Application Publ. No. 20100043095 to Wei, which is hereby incorporated by reference in its entirety).

Once the peptides of the present invention are recovered, they can be used to prepare a composition that includes a carrier, and one or more additives selected from the group consisting of a bacteriocidal or biocidal agent, a protease inhibitor, a non-ionic surfactant, a fertilizer, an herbicide, an insecticide, a fungicide, a nematicide, biological inoculants, plant regulators, and mixtures thereof.

In certain embodiments, the compositions include greater than about 1 nM of the peptide, greater than about 10 nM of the peptide, greater than about 20 nM of the peptide, greater than about 30 nM of the peptide, greater than about 40 nM of the peptide, greater than about 50 nM of the peptide, greater than about 60 nM of the peptide, greater than about 70 nM of the peptide, greater than 80 about nM of the peptide, greater than about 90 nM of the peptide, greater than about 100 nM of the peptide, greater than about 150 nM of the peptide, greater than about 200 nM of the peptide, or greater than about 250 nM of the peptide. In certain embodiments, the compositions include less than about 1 nM of the peptide. For example, certain peptides can be present at a concentration of less than about 2 ng/ml, less than about 1.75 ng/ml, less than about 1.5 ng/ml, less than about 1.25 ng/ml, less than about 1.0 ng/ml, less than about 0.75 ng/ml, less than about 0.5 ng/ml, less than about 0.25 ng/ml, or even less than about 0.1 ng/ml.

Suitable carriers include water, aqueous solutions optionally containing one or more co-solvents, slurries, and solid carrier particles. Exemplary solid carriers include mineral earths such as silicates, silica gels, talc, kaolins, limestone, lime, chalk, bole, loess, clays, dolomite, diatomaceous earth, calcium sulfate, magnesium sulfate, magnesium oxide, ground synthetic materials, and products of vegetable origin, such as cereal meal, tree bark meal, wood meal and nutshell meal, cellulose powders, starches and starch derivatives, as well as other mono-, di-, and poly-saccharides.

Suitable fertilizers include, without limitation, ammonium sulfate, ammonium phosphate, ammonium nitrate, ureas, and combinations thereof.

Suitable insecticides include, without limitation, members of the neonicotinoid class such as imidicloprid, clothianidin, and thiamethoxam; members of the organophosphate class such as chlorpyrifos and malathion; members of the pyrethroid class such as permethrin; other natural insecticides such as nicotine, nornicotine, and pyrethrins; members of the carbamate class such as aldicarb, carbofuran, and carbaryl; members of the macrocyclic lactone class such as various abamectin, avermectin, and ivermectin products; members of the diamide class such as chlorantraniliprole, cyantraniliprole, and flubendiamide; chitin synthesis inhibitors, particularly those of the benzoylurea class such as lufenuron and diflubenzuron; and any combination thereof, including combinations of two or more, three or more, or four or more insecticides. Additional insecticides are listed in the Compendium of Pesticide Common Names, which is database operated by Alan Wood and available in electronic form at the alanwood.net internet site.

Suitable fungicides include, without limitation, members of the strobilurin class such as azoxystrobin, pyraclostrobin, trifloxystrobin, picoxystrobin, and fluoxastrobin; members of the triazole class such as ipconazole, metconazole, tebuconazole, triticonazole, tetraconazole, difenoconazole, flutriafol, propiconazole and prothioconazole; members of the succinate dehydrogenase class such as carboxin, fluxapyroxad, boscalid and sedaxane: members of the phenylamide class such as metalaxyl, mefenoxam, benalaxyl, and oxadiyxl; members of the phenylpyrrole class such as fludioxonil; members of the phthalimide class such as captan; members of the dithiocarbamate class such as mancozeb and thiram; members of the benzimidazole class such as thiabendazole; and any combination thereof, including combinations of two or more, three or more, or four or more fungicides. Additional fungicides are listed in the Compendium of Pesticide Common Names, which is a database operated by Alan Wood and available in electronic form at the alanwood.net internet site.

Suitable nematicides include, without limitation, chemicals of the carbamate class such as aldicarb, aldoxycarb, oxamyl, carbofuran, and cleothocarb; and chemicals of the organophosphate class such as thionazin, ethoprophos, fenamiphos, fensulfothion, terbufos, isazofos, and ebufos. Additional nematicides are listed in the Compendium of Pesticide Common Names, which is a database operated by Alan Wood and available in electronic form at the alanwood.net internet site.

Suitable bactericides include, without limitation, those based on dichlorophene and benzylalcohol hemi formal (Proxel® from ICI or Acticide® RS from Thor Chemie and Kathon® MK from Rohm & Haas) and isothiazolinone derivatives such as alkylisothiazolinones and benzisothiazolinones (Acticide® MBS from Thor Chemie; Proxel® GXL from ICI). Additional bactericides are listed in the Compendium of Pesticide Common Names, which is a database operated by Alan Wood and available in electronic form at the alanwood.net internet site.

Suitable inoculants include, without limitation, Bradyrhizobium spp., particularly Bradyrhizobium japonicum (BASF Vault® products), Bacillus subtilis, Bacillus firmus, Bacillus pumilis, Streptomyces lydicus, Trichoderma spp., Pasteuria spp., other cultures of rhizobial cells (BASF Nodulator® and Rhizo-Flo®), and any combination thereof, including combinations of two or more, three or more, or four or more inoculants.

Plant regulators are chemical substances, either natural or synthetic, that either stimulate or inhibit plant biochemical signaling. These are usually, but not exclusively, recognized by receptors on the surface of the cell, causing a cascade of reactions in the cell. Suitable plant regulators include, without limitation, ethephon; ethylene; salicylic acid; acetylsalicylic acid; jasmonic acid; methyl jasmonate; methyl dihydrojasmonate; chitin; chitosan; abscisic acid; any auxin compound or inhibitor, including but not limited to (4-chlorophenoxy)acetic acid, (2,4-dichlorophenoxy)acetic acid, and 2,3,5-triiodobenzoic acid; any cytokinin, including but not limited to kinetin and zeatin; gibberellins; brassinolide; and any combination thereof, including combinations of two or more, three or more, or four or more regulators.

Other suitable additives include buffering agents, wetting agents, coating agents, and abrading agents. These materials can be used to facilitate application of the compositions in accordance with the present invention. In addition, the compositions can be applied to plant seeds with other conventional seed formulation and treatment materials, including clays and polysaccharides.

Compositions or systems use for plant seed treatment include: one or more of the peptides of the present invention, preferably though not exclusively one or more of peptides p4-14s-9a (SEQ ID NO: 57), p4-14s-12d (SEQ ID NO: 59), p14 (SEQ ID NO: 113), p14a (SEQ ID NO: 114), p14-22E,26E (SEQ ID NO: 23), p1-29 (SEQ ID NO: 130), and p4-14S-16S (SEQ ID NO: 55) in combination with one or more insecticides, nematicides, fungicides, other inoculants, or other plant regulators, including combinations of multiple insecticides, or multiple nematicides, multiple fungicides, multiple other inoculants, or multiple plant regulators. Suitable insecticides, nematicides, fungicides, inoculants, and plant regulators for these combination treatments include those identified above. These compositions are presented in the form of a single composition at the time of seed treatment. In contrast, a system used for seed treatment may involve multiple treatments, e.g., a composition containing the peptides is used in one treatment and a composition containing the one or more insecticides, nematicides, fungicides, plant regulators and/or bactericides, is used in a separate treatment. In the latter embodiment, both of these treatments are carried out at about the same time, i.e., before planting or at about the time of planting.

One such example includes one or more of peptides of the present invention, including (without limitation) one or more of peptides p4-14s-9a (SEQ ID NO: 57), p4-14s-12d (SEQ ID NO: 59), p14 (SEQ ID NO: 113), p14a (SEQ ID NO: 114), p14-22E,26E (SEQ ID NO: 23), p1-29 (SEQ ID NO: 130), and p4-14S-16S (SEQ ID NO: 55), in combination with one of Poncho™ (clothianidin) available from Bayer Crop Science, Poncho™ VOTiVO (clothianidin and Bacillus firmus biological nematicide) available from Bayer Crop Science, and Gaucho™ (imidicloprid) available from Bayer Crop Science.

Another example includes one or more of peptides of the present invention, including (without limitation) one or more of peptides p4-14s-9a (SEQ ID NO: 57), p4-14s-12d (SEQ ID NO: 59), p14 (SEQ ID NO: 113), p14a (SEQ ID NO: 114), p14-22E,26E (SEQ ID NO: 23), p1-29 (SEQ ID NO: 130), and p4-14S-16S (SEQ ID NO: 55), in combination with one of Cruiser™ (thiamethoxam) available from Syngenta, CruiserMaxx™ (thiamethoxam, mefenoxam, and fludioxynil) available from Syngenta, Cruiser Extreme™ (thiamethoxam, mefenoxam, fludioxynil, and azoxystrobin) available from Syngenta, Avicta™ (thiamethoxam and abamectin) available from Syngenta, and Avicta™ Complete (thiamethoxam, abamectin, and Clariva Complete™ which contains the Pasteuria nishizawae—Pn1 biological inoculant) available from Syngenta, and Avicta Complete™ Corn (thiamethoxam, mefenoxam, fludioxynil, azoxystrobin, thiabendazole and abamectin) available from Syngenta.

Another example includes one or more of peptides of the present invention, including (without limitation) one or more of peptides p4-14s-9a (SEQ ID NO: 57), p4-14s-12d (SEQ ID NO: 59), p14 (SEQ ID NO: 113), p14a (SEQ ID NO: 114), p14-22E,26E (SEQ ID NO: 23), p1-29 (SEQ ID NO: 130), and p4-14S-16S (SEQ ID NO: 55), in combination with one of Vault Liquid plus Integral (Bradyrhizobium species and Bacillus subtilis strain MBI 600 inoculants) available from BASF, Vault NP (Bradyrhizobium japonicum inoculant) available from BASF, and Subtilex NG (Bacillus subtilis biological inoculant) available from BASF.

The present invention further relates to methods of imparting disease resistance to plants, enhancing plant growth, effecting pest control (including insects and nematodes), imparting biotic or abiotic stress tolerance to plants, and/or modulating plant biochemical signaling. These methods involve applying an effective amount of an isolated peptide of the invention, or a composition of the invention to a plant or plant seed or the locus where the plant is growing or is expected to grow. As a consequence of such application, the peptide contacts cells of the plant or plant seed, and induces in the plant or a plant grown from the plant seed disease resistance, growth enhancement, tolerance to biotic stress, tolerance to abiotic stress, or altered biochemical signaling. Alternatively, the peptide or composition of the invention can be applied to plants such that seeds recovered from such plants themselves are able to impart disease resistance in plants, to enhance plant growth, to affect insect control, to impart tolerance to biotic or abiotic stress, and/or to modulate biochemical signaling.

In these embodiments, it is also possible to select plants or plant seeds or the locus to which the isolated peptide or composition of the invention is applied. For example, for fields known to contain a high nematode content, the plants or plant seeds to be grown in such fields, or the fields (locus), can be selectively treated by applying the isolated peptide or composition of the invention as described herein; whereas no such treatment may be necessary for plants or plant seeds grown in fields containing low nematode content. Similarly, for fields having reduced irrigation, the plants or plant seeds to be grown in such fields, or the fields (locus), can be selectively treated by applying the isolated peptide or composition of the invention as described herein; whereas no such treatment may be necessary for plants or plant seeds grown in fields having adequate irrigation. Likewise, for fields prone to flooding, the plants or plant seeds to be grown in such fields, or the fields (locus), can be selectively treated by applying the isolated peptide or composition of the invention as described herein; whereas no such treatment may be necessary for plants or plant seeds grown in fields that are not prone to flooding. As yet another example of such selection, for fields prone to insect attack at certain times of the growing season, the plants or plant seeds to be grown in such fields, or the fields (locus), can be selectively treated by applying the isolated peptide or composition of the invention as described herein; whereas the same field may not be treated at ineffective times of the growing season or other fields that are not prone to such attack may go untreated. Such selection steps can be carried out when practicing each of the methods of use described herein, i.e., imparting disease resistance to plants, enhancing plant growth, effecting pest control (including insects and nematodes), imparting biotic or abiotic stress tolerance to plants, and/or modulating plant biochemical signaling.

As an alternative to applying an isolated peptide or a composition containing the same to plants or plant seeds in order to impart disease resistance in plants, to effect plant growth, to control insects, to impart stress resistance, and/or modulated biochemical signaling to the plants or plants grown from the seeds, transgenic plants or plant seeds can be utilized. When utilizing transgenic plants, this involves providing a transgenic plant transformed with a DNA molecule encoding a peptide of the invention and growing the plant under conditions effective to permit that DNA molecule to impart disease resistance to plants, to enhance plant growth, to control insects, and/or to impart tolerance to biotic or abiotic stress. Alternatively, a transgenic plant seed transformed with a DNA molecule encoding a peptide of the invention can be provided and planted in soil. A plant is then propagated from the planted seed under conditions effective to permit that DNA molecule to express the peptide and thereby impart disease resistance to the transgenic plant, to enhance plant growth, to control insects, and/or to impart tolerance to biotic or abiotic stress.

In these embodiments, it is also possible to select transgenic plants or plant seeds for carrying out the present invention. For example, for fields known to contain a high nematode content, the transgenic plants or plant seeds can be selectively grown in such fields; whereas non-transgenic plants or plant seeds can be grown in fields containing low nematode content. Similarly, for fields having reduced irrigation, the transgenic plants or plant seeds can be selectively grown in such fields; whereas non-transgenic plants or plant seeds can be grown in fields having adequate irrigation. Likewise, for fields prone to flooding, the transgenic plants or plant seeds can be grown in such fields; whereas non-transgenic plants or plant seeds can be grown in fields that are not prone to flooding. As yet another example of such selection, for fields prone to insect attack at certain times of the growing season, the transgenic plants or plant seeds can be selectively grown in such fields; whereas non-transgenic plants or plant seeds can be grown in fields that are not prone to such insect attack. Such selection steps can be carried out when practicing each of the methods of use described herein, i.e., imparting disease resistance to plants, enhancing plant growth, effecting pest control (including insects and nematodes), imparting biotic or abiotic stress tolerance to plants, and/or modulating plant biochemical signaling.

The present invention further relates to methods of improving desiccation resistance for cuttings removed from ornamental plants, post-harvest disease resistance or desiccation resistance to fruit or vegetables harvested from plants, and/or improved longevity of fruit or vegetable ripeness for fruit or vegetables harvested from plants. These methods involve applying an effective amount of an isolated peptide of the present invention or a composition according to the present invention to a plant or the locus where the plant is growing. As a consequence of such application, the peptide contacts cells of the plant or plant seed, and induces desiccation resistance for cuttings removed from ornamental plants, post-harvest disease resistance or desiccation resistance to fruit or vegetables harvested from plants, and/or improved longevity of fruit or vegetable ripeness for fruit or vegetables harvested from plants. Alternatively, an effective amount of an isolated peptide of the present invention or a composition according to the present invention can be applied to a harvested fruit or vegetable. As a consequence of such application, the peptide contacts cells of the harvested fruit or vegetable, and induces post-harvest disease resistance or desiccation resistance to the treated fruit or vegetables, and/or improved longevity of fruit or vegetable ripeness for the treated fruit or vegetables.

In these embodiments, it is also possible to select plants, cuttings, fruits, vegetables, or the locus to which the isolated peptide or composition of the invention is applied. For example, for harvested cuttings or fruit or vegetables that are being shipped great distances or stored for long periods of time, then these can be selectively treated by applying the isolated peptide or composition of the invention as described herein; whereas harvested cuttings or fruit or vegetables that are being shipped locally and intended to be consumed without substantially periods of storage can be excluded from such treatment.

As an alternative to applying an isolated peptide or a composition containing the same to plants or plant seeds in order to induce desiccation resistance to cuttings removed from ornamental plants, post-harvest disease resistance or desiccation resistance to fruit or vegetables harvested from plants, and/or improved longevity of fruit or vegetable ripeness for fruit or vegetables harvested from plants, transgenic plants or plant seeds can be utilized. When utilizing transgenic plants, this involves providing a transgenic plant transformed with a DNA molecule encoding a peptide of the invention and growing the plant under conditions effective to permit that DNA molecule to induce desiccation resistance for cuttings removed from ornamental plants, post-harvest disease resistance or desiccation resistance to fruit or vegetables harvested from the transgenic plants, and/or improved longevity of fruit or vegetable ripeness for fruit or vegetables harvested from the transgenic plants. Alternatively, a transgenic plant seed transformed with a DNA molecule encoding a peptide of the invention can be provided and planted in soil. A plant is then propagated from the planted seed under conditions effective to permit that DNA molecule to express the peptide and thereby induce desiccation resistance for cuttings removed from ornamental plants, post-harvest disease resistance or desiccation resistance to fruit or vegetables harvested from the transgenic plants, and/or improved longevity of fruit or vegetable ripeness for fruit or vegetables harvested from the transgenic plants.

In these embodiments, it is also possible to select transgenic plants or plant seeds for carrying out the present invention. For example, transgenic plants or plant seeds can be selected for growing when it is known that harvested cuttings or fruit or vegetables are intended to be shipped great distances or stored for long periods of time post-harvest; whereas non-transgenic plants or plant seeds can be selected for growing when it is known that harvested cuttings or fruit or vegetables are intended to be shipped locally and/or consumed without substantially periods of storage.

Suitable plants include dicots and monocots, including agricultural, silvicultural, ornamental and horticultural plants, whether in a natural or genetically modified form. Exemplary plants include, without limitation, alfalfa, apple, apricot, asparagus, avocados, bananas, barley, beans, beech (Fagus spec.), begonia, birch, blackberry, blueberry, cabbage, camphor, canola, carrot, castor oil plant, cherry, cinnamon, citrus, cocoa bean, coffee, corn, cotton, cucumber, cucurbit, eucalyptus, fir, flax, fodder beet, fuchsia, garlic, geranium, grapes, ground nut, hemp, hop, juneberry, juncea (Brassica juncea), jute, lentil, lettuce, linseed, melon, mustard, nectarine, oak, oats, oil palm, oil-seed rape, olive, onion, paprika, pea, peach, pear, pelargonium, peppers, petunia, pine (Pinus spec.), plum, poplar (Populus spec.), pome fruit, potato, rape, raspberry, rice, rubber tree, rye, sorghum, soybean, spinach, spruce, squash, strawberry, sugar beet, sugar cane, sunflower, tea, teak, tobacco, tomato, triticale, turf, watermelon, wheat and willow (Salix spec.), Arabidopsis thaliana, Saintpaulia, poinsettia, chrysanthemum, carnation, and zinnia.

With respect to modified biochemical signaling, this includes both enhancement of certain plant biochemical pathways and diminishment of certain other plant biochemical pathways. Biochemical signaling pathways that can be altered in accordance with the present invention include gene expression and protein production, production of metabolites, and production of signaling molecules/secondary metabolites. Exemplary biochemical signaling pathways and their modifications include, without limitation, induction of nitric oxide production, peroxide production, and other secondary metabolites; agonist of the ethylene signaling pathway and induction of ethylene-responsive gene expression (see Dong et al., Plant Phys. 136:3628-3638 (2004); Li et al., Planta 239:831-46 (2014); Chang et al., PLoS One 10,e0125498 (2015), each of which is hereby incorporated by reference in its entirety); agonist of the salicylic acid signaling pathway and induction of salicylic acid-responsive gene expression (see Dong et al., Plant J. 20:207-215 (1999), which is hereby incorporated by reference in its entirety); agonist of the abscisic acid pathway and induction of abscisic acid-responsive gene expression (see Dong et al., Planta 221: 313-327 (2005), which is hereby incorporated by reference in its entirety); agonist of the gibberellin signaling pathway and induction of gibberellin-responsive gene expression (see Li et al., Planta 239:831-46 (2014), which is hereby incorporated by reference in its entirety); antagonist of jasmonic acid signaling and inhibiting expression of jasmonic acid-responsive genes (see Dong et al., Plant Phys. 136:3628-3638 (2004), which is hereby incorporated by reference in its entirety); inducing protease inhibitor expression (see Laluk and Mengiste, Plant J. 68:480-494 (2011); Xia et al., Chin. Sci. Bull 56: 2351-2358 (2011), each of which is hereby incorporated by reference in its entirety); inducing reactive oxygen species production in plant tissues; inducing immune-related and antimicrobial peptide production, such as, without limitation, peroxidase, superoxide dismutase, chitinase, and β-1,3-glucanase (Wang et al., J. Agric. Food Chem. 59:12527-12533 (2011), which is hereby incorporated by reference in its entirety); and inducing expansion gene expression and production (see Li et al., Planta 239:831-46 (2014), which is hereby incorporated by reference in its entirety).

With respect to disease resistance, absolute immunity against infection may not be conferred, but the severity of the disease is reduced and symptom development is delayed. Lesion number, lesion size, and extent of sporulation of fungal pathogens are all decreased. This method of imparting disease resistance has the potential for treating previously untreatable diseases, treating diseases systemically which might not be treated separately due to cost, and avoiding the use of infectious agents or environmentally harmful materials.

The method of imparting pathogen resistance to plants in accordance with the present invention is useful in imparting resistance to a wide variety of pathogens including viruses, bacteria, and fungi. Resistance, inter alia, to the following viruses can be achieved by the method of the present invention: Tobacco mosaic virus and Tomato mosaic virus. Resistance, inter alia, to the following bacteria can also be imparted to plants in accordance with present invention: pathogenic Pseudomonas spp., pathogenic Erwinia spp., pathogenic Xanthomonas spp., and pathogenic Ralstonia spp. Plants can be made resistant, inter alia, to the following fungi by use of the method of the present invention: Fusarium spp. and Phytophthora spp.

With regard to the use of the peptides or compositions of the present invention to enhance plant growth, various forms of plant growth enhancement or promotion can be achieved. This can occur as early as when plant growth begins from seeds or later in the life of a plant. For example, plant growth according to the present invention encompasses greater yield, increased plant vigor, increased vigor of seedlings (i.e., post-germination), increased plant weight, increased biomass, increased number of flowers per plant, higher grain and/or fruit yield, increased quantity of seeds produced, increased percentage of seeds germinated, increased speed of germination, increased plant size, decreased plant height (for wheat), greater biomass, more and bigger fruit, earlier fruit coloration, earlier bud, fruit and plant maturation, more tillers or side shoots, larger leaves, delayed leaf senescence, increased shoot growth, increased root growth, altered root/shoot allocation, increased protein content, increased oil content, increased carbohydrate content, increased pigment content, increased chlorophyll content, increased total photosynthesis, increased photosynthesis efficiency, reduced respiration (lower O₂ usage), compensation for yield-reducing treatments, increased durability of stems (and resistance to stem lodging), increased durability of roots (and resistance to root lodging), better plant growth in low light conditions, and combinations thereof. As a result, the present invention provides significant economic benefit to growers. For example, early germination and early maturation permit crops to be grown in areas where short growing seasons would otherwise preclude their growth in that locale. Increased percentage of seed germination results in improved crop stands and more efficient seed use. Greater yield, increased size, and enhanced biomass production allow greater revenue generation from a given plot of land.

With regard to the use of the peptides or compositions of the present invention to control pests (including but not limited to insects and nematodes, which are biotic stressors), such pest control encompasses preventing pests from contacting plants to which the peptide or composition of the invention has been applied, preventing direct damage to plants by feeding injury, causing pests to depart from such plants, killing pests proximate to such plants, interfering with insect larval feeding on such plants, preventing pests from colonizing host plants, preventing colonizing insects from releasing phytotoxins, interfering with egg deposition on host plants, etc. The present invention also prevents subsequent disease damage to plants resulting from pest infection.

The present invention is effective against a wide variety of insects (biotic stressors). European corn borer is a major pest of corn (dent and sweet corn) but also feeds on over 200 plant species including green, wax, and lima beans and edible soybeans, peppers, potato, and tomato plus many weed species. Additional insect larval feeding pests which damage a wide variety of vegetable crops include the following: beet armyworm, cabbage looper, corn ear worm, fall armyworm, diamondback moth, cabbage root maggot, onion maggot, seed corn maggot, pickleworm (melonworm), pepper maggot, and tomato pinworm. Collectively, this group of insect pests represents the most economically important group of pests for vegetable production worldwide. The present invention is also effective against nematodes, another class of economically important biotic stressors. Soybean Cyst Nematode (Heterodera glycines) is a major pest of soybeans. Reniform Nematode (Rotylenchulus reniformis) is a major pest of cotton as can parasitize additional crop species, notably soy and corn. Additional nematode pests include the root knot nematodes of the genus Meloidogyne (particularly in cotton, wheat, and barley), cereal cyst nematodes of the genus Heterodera (particularly in soy, wheat, and barley), root lesion nematodes of the genus Pratylenchus, seed gall nematodes of the genus Anguina (particularly in wheat, barley, and rye), and stem nematodes of the genus Ditylenchus. Other biotic stressors include arachnids, weeds, and combinations thereof.

With regard to the use of the peptides or compositions of the present invention to impart abiotic stress resistance to plants, such abiotic stress encompasses any environmental factor having an adverse effect on plant physiology and development. Examples of such environmental stress include climate-related stress (e.g., drought, flood, frost, cold temperature, high temperature, excessive light, and insufficient light), air pollution stress (e.g., carbon dioxide, carbon monoxide, sulfur dioxide, NO_(x), hydrocarbons, ozone, ultraviolet radiation, acidic rain), chemical (e.g., insecticides, fungicides, herbicides, heavy metals), nutritional stress (e.g., over- or under-abundance of fertilizer, micronutrients, macronutrients, particularly potassium, nitrogen derivatives, and phosphorus derivatives), and improved healing response to wounding. Use of peptides of the present invention imparts resistance to plants against such forms of environmental stress.

A further aspect of the present invention relates to the use of the peptides of the present invention as a safener in combination with one or more of the active agents (i.e., in a composition or in separate compositions) for the control of aquatic weeds in a body of water as described in U.S. Publ. No. 20150218099 to Mann, which is hereby incorporated by reference in its entirety.

Yet another aspect of the present invention relates to the use of the peptides of the present invention as a plant strengthener in a composition for application to plants grown under conditions of reduced water irrigation, which composition also includes at least one antioxidant and at least one radiation manager, and optionally at least one plant growth regulator, as described in U.S. Publ. No. 20130116119 to Rees et al., which is hereby incorporated by reference in its entirety.

The methods of the present invention involving application of the peptide or composition can be carried out through a variety of procedures when all or part of the plant is treated, including leaves, stems, roots, propagules (e.g., cuttings), fruit, etc. This may (but need not) involve infiltration of the peptide into the plant. Suitable application methods include high or low pressure spraying, injection, and leaf abrasion proximate to when peptide application takes place. When treating plant seeds, in accordance with the application embodiment of the present invention, the hypersensitive response elicitor protein or polypeptide can be applied by low or high pressure spraying, coating, immersion (e.g., soaking), or injection. Other suitable application procedures can be envisioned by those skilled in the art provided they are able to effect contact of the hypersensitive response elicitor polypeptide or protein with cells of the plant or plant seed. Once treated with the peptides or compositions of the present invention, the seeds can be planted in natural or artificial soil and cultivated using conventional procedures to produce plants. After plants have been propagated from seeds treated in accordance with the present invention, the plants may be treated with one or more applications of the peptides or compositions of the invention to impart disease resistance to plants, to enhance plant growth, to control insects on the plants, to impart biotic or abiotic stress tolerance, to improve desiccation resistance of removed cuttings, to impart post-harvest disease resistance or desiccation resistance to harvested fruit or vegetables, and/or improved longevity of fruit or vegetable ripeness for harvested fruit or vegetables.

The peptides or compositions of the invention can be applied to plants or plant seeds in accordance with the present invention alone or in a mixture with other materials. Alternatively, the peptides or compositions can be applied separately to plants with other materials being applied at different times.

In the alternative embodiment of the present invention involving the use of transgenic plants and transgenic seeds, a peptide of the invention need not be applied topically to the plants or seeds. Instead, transgenic plants transformed with a DNA molecule encoding a peptide of the invention are produced according to procedures well known in the art. A vector suitable for expression in plants (i.e., containing translation and transcription control sequences operable in plants) can be microinjected directly into plant cells by use of micropipettes to transfer mechanically the recombinant DNA. Crossway, Mol. Gen. Genetics, 202:179-85 (1985), which is hereby incorporated by reference in its entirety. The genetic material may also be transferred into the plant cell using polyethylene glycol. Krens, et al., Nature, 296:72-74 (1982), which is hereby incorporated by reference in its entirety.

Another approach to transforming plant cells with a gene encoding the peptide of the invention is particle bombardment (also known as biolistic transformation) of the host cell. This can be accomplished in one of several ways. The first involves propelling inert or biologically active particles at cells. This technique is disclosed in U.S. Pat. Nos. 4,945,050, 5,036,006, and 5,100,792, all to Sanford et al., which are hereby incorporated by reference. Generally, this procedure involves propelling inert or biologically active particles at the cells under conditions effective to penetrate the outer surface of the cell and to be incorporated within the interior thereof. When inert particles are utilized, the vector can be introduced into the cell by coating the particles with the vector containing the heterologous DNA. Alternatively, the target cell can be surrounded by the vector so that the vector is carried into the cell by the wake of the particle. Biologically active particles (e.g., dried bacterial cells containing the vector and heterologous DNA) can also be propelled into plant cells.

Yet another method of introduction is fusion of protoplasts with other entities, either minicells, cells, lysosomes or other fusible lipid-surfaced bodies. Fraley, et al., Proc. Natl. Acad. Sci. USA, 79:1859-63 (1982), which is hereby incorporated by reference in its entirety. The DNA molecule may also be introduced into the plant cells by electroporation. Fromm et al., Proc. Natl. Acad. Sci. USA, 82:5824 (1985), which is hereby incorporated by reference in its entirety. In this technique, plant protoplasts are electroporated in the presence of plasmids containing the expression cassette. Electrical impulses of high field strength reversibly permeabilize biomembranes allowing the introduction of the plasmids. Electroporated plant protoplasts reform the cell wall, divide, and regenerate.

Another method of introducing the DNA molecule into plant cells is to infect a plant cell with Agrobacterium tumefaciens or A. rhizogenes previously transformed with the gene. Under appropriate conditions known in the art, the transformed plant cells are grown to form shoots or roots, and develop further into plants. Generally, this procedure involves inoculating the plant tissue with a suspension of bacteria and incubating the tissue for 48 to 72 hours on regeneration medium without antibiotics at 25-28° C. Agrobacterium is a representative genus of the gram-negative family Rhizobiaceae. Its species are responsible for crown gall (A. tumefaciens) and hairy root disease (A. rhizogenes). The plant cells in crown gall tumors and hairy roots are induced to produce amino acid derivatives known as opines, which are catabolized only by the bacteria. The bacterial genes responsible for expression of opines are a convenient source of control elements for chimeric expression cassettes. In addition, assaying for the presence of opines can be used to identify transformed tissue. Heterologous genetic sequences can be introduced into appropriate plant cells, by means of the Ti plasmid of A. tumefaciens or the Ri plasmid of A. rhizogenes. The Ti or Ri plasmid is transmitted to plant cells on infection by Agrobacterium and is stably integrated into the plant genome. J. Schell, Science, 237:1176-83 (1987), which is hereby incorporated by reference in its entirety.

After transformation, the transformed plant cells must be regenerated. Plant regeneration from cultured protoplasts is described in Evans et al., Handbook of Plant Cell Cultures, Vol. 1: (MacMillan Publishing Co., New York, 1983); and Nasil I. R. (ed.), Cell Culture and Somatic Cell Genetics of Plants, Acad. Press, Orlando, Vol. 1, 1984, and Vol. III (1986), which are hereby incorporated by reference in their entirety.

It is known that practically all plants can be regenerated from cultured cells or tissues. Means for regeneration vary from species to species of plants, but generally a suspension of transformed protoplasts or a petri plate containing transformed explants is first provided. Callus tissue is formed and shoots may be induced from callus and subsequently rooted. Alternatively, embryo formation can be induced in the callus tissue. These embryos germinate as natural embryos to form plants. The culture media will generally contain various amino acids and hormones, such as auxin and cytokinins. It is also advantageous to add glutamic acid and proline to the medium, especially for such species as corn and alfalfa. Efficient regeneration will depend on the medium, on the genotype, and on the history of the culture. If these three variables are controlled, then regeneration is usually reproducible and repeatable.

After the expression cassette is stably incorporated in transgenic plants, it can be transferred to other plants by sexual crossing. Any of a number of standard breeding techniques can be used, depending upon the species to be crossed.

Once transgenic plants of this type are produced, the plants themselves can be cultivated in accordance with conventional procedure with the presence of the gene encoding the hypersensitive response elicitor resulting in disease resistance, enhanced plant growth, control of insects on the plant, abiotic or biotic stress tolerance, improved desiccation resistance of removed cuttings, post-harvest disease resistance or desiccation resistance in harvested fruit or vegetables, and/or improved longevity of fruit or vegetable ripeness for harvested fruit or vegetables.

Alternatively, transgenic seeds are recovered from the transgenic plants. These seeds can then be planted in the soil and cultivated using conventional procedures to produce transgenic plants. The transgenic plants are propagated from the planted transgenic seeds under conditions effective to impart disease resistance to plants, to enhance plant growth, to control insects, to impart abiotic or biotic stress tolerance, to improve desiccation resistance of removed cuttings, to impart post-harvest disease resistance or desiccation resistance in harvested fruit or vegetables, and/or to impart improved longevity of fruit or vegetable ripeness for harvested fruit or vegetables.

When transgenic plants and plant seeds are used in accordance with the present invention, they additionally can be treated with the same materials as are used to treat the plants and seeds to which a peptide of the invention or composition of the invention is applied. These other materials, including peptides or composition of the invention, can be applied to the transgenic plants and plant seeds by the above-noted procedures, including high or low pressure spraying, injection, coating, and immersion. Similarly, after plants have been propagated from the transgenic plant seeds, the plants may be treated with one or more applications of the peptides or compositions of the invention to impart disease resistance, enhance growth, control insects, abiotic or biotic stress tolerance, desiccation resistance of removed cuttings, post-harvest disease resistance or desiccation resistance in harvested fruit or vegetables, and/or improved longevity of fruit or vegetable ripeness for harvested fruit or vegetables.

Such transgenic plants may also be treated with conventional plant treatment agents, e.g., bacteriocidal or biocidal agents, protease inhibitors, non-ionic surfactants, fertilizers, herbicides, insecticides, fungicides, nematicides, biological inoculants, plant regulators, and mixtures thereof, as described above.

EXAMPLES

The following examples are provided to illustrate embodiments of the present invention but are by no means intended to limit its scope.

Example 1—Hypersensitive Response Analysis

HR in tobacco was tested as described in Wei, Science 257:85-88 (1992), which is hereby incorporated by reference in its entirety. Briefly, peptides were dissolved at a concentration of 500 μg/ml in aqueous solution. Four serial dilutions were performed with an equal volume of water, yielding peptide samples at 500, 250, 125, 62.5, 31.25 μg/ml peptide solutions. Nicotiana tabacum cultivar xanthi plants were used at 5-7 weeks old (preflowering). Leaves were lightly punctured with a toothpick in a middle leaf panel. Peptide solutions were then infused via needle-less syringe into the wound, filling the panel. Each peptide sample was infused into a leaf of 2 different plants. The leaves were observed and scored over the next 48 hours for withering and browning, lesions typical of programmed cell death.

Hypersensitive Response testing was performed on many peptides and determined to be negative. Some peptides have yet to be tested, designed as “to be determined” or “TBD” in Table 18 below, but are expected to be HR-negative based on the results for closely related peptides.

TABLE 18 Summary of Hypersensitive Response Results SEQ SEQ ID Tobacco ID Tobacco Name NO: HR Name NO: HR P1-13P-20P 164 — P14 113 — P1-29 130 TBD P14-22L, 26L 115 — P1-31 131 TBD P14-22L, 26E 19 — P3-5 156 — P14-22A, 26L 20 TBD P3-9 158 — P14-22A, 26E 21 TBD P3-10 159 — P14-22E, 26L 22 TBD P4-14S-9A 57 — P14-22E, 26E 23 TBD P4-14S-9D 58 — P14-22L, 26A 26 — P4-14S-9S 52 — P14-22A, 26A 27 TBD P4-14S-9Y 53 — P14-22L, 25-26A 28 TBD P4-14S-12D 59 — P14-22L, 28-29A 29 TBD P4-14s-13D 48 — P14-22L, 32-33A 30 TBD P4-14S-13F 134 — P14-22L, 26, 29A 31 TBD P4-14S-13V 133 — P14-22L, 28, 32A 32 TBD P4-14S-13Q 54 — P14-dc2 122 TBD P4-14S-16S 55 — P14-dc4 123 TBD P4-14S-17D 49 — P14a 114 — P4-14S-20S 56 — P15-60 150 — P4-14S-21D 50 — P15-61 151 — P4-d10, 14, 18 62 — P15-62 148 TBD P4-d18 51 — P15-63 149 TBD P4-i10A, 14A, 18A 68 — P18-8 142 TBD P4-i10A 65 — P18-9 143 TBD P4-i14A 66 — P19-9 144 — P4-i18A 67 — P19-10 145 — P4-i21Q 63 — P19-12 146 — P4-i21H 64 — P19-13 147 — P4-111 132 — P6a-15D 199 TBD P4-116 140 TBD P6a-11S 204 TBD P4-117 141 TBD P15b-12S 188 TBD P14d-7D 208 TBD P14d-17D 213 TBD P14d-10D 209 TBD P14d-18D 214 TBD P14d-11D 210 TBD P14d-7S 215 TBD P14d-14D 211 TBD P14f-17S 45 TBD P14d-15D 212 TBD TBD = To be determined.

Example 2—Peroxide Response Analysis

The ferric-xylenol orange complex assay for hydrogen peroxide (Gay et al., Analytical Biochemistry 273:149-55 (1999), which is hereby incorporated by reference in its entirety) was used to determine peroxide production by plant leaf tissue. Briefly, reagent A was prepared by mixing 10 mg of ferrous ammonium sulfate with 133 uL of sulfuric acid in a total volume of 1 mL with water. Reagent B was prepared by mixing 2 g of sorbitol with 9.34 mg of xylenol orange in 80 ml of water. 1M hydrochloric acid was slowly added until the solution turned yellow. The solution was then diluted with water to a total volume of 100 mL, and stored in a dark bottle at 4° C.

Leaves from either tobacco plants (plants grown to 6 true leaves) or soy plants (plants grown to 6 true leaves) were used for the assay. The leaf was first removed from the plant and placed on a paper towel. 0.5 cm leaf tissue circles were then removed from the leaf using a leather punch tool. These discs were then placed into the wells of a 96-well plate. 250 ml of water was added to each disc. The plate was covered with parafilm and rested for 12 hours in the dark. The excess water was then removed and the wells washed with an additional 250 uL of water. The washes were then removed from the wells and replaced with 105 uL of a 0.5 ug/ml solution of peptide in water or water blank, generally in quadruplicate. Where peptide solubility was a problem, pH buffer was added to both the blank and peptide samples. Leaf discs were incubated with the peptides for one hour under fluorescent lighting. 50 ul of the solution from each leaf sample was removed to a new well for chemical analysis.

Just prior to analysis, reagents A and B were freshly mixed in a 1:100 ratio to produce the assay reagent. 200 ul of this mixture was added to each well containing 50 ul of leaf-treated solution. The plate was incubated in the dark for 20 minutes and the absorbance at 595 nm was detected. Results were analyzed using a two-tailed Student's T-test. The results were divided into several response classes. XR++ indicated a positive response with absorbance >0.05 units above the negative control and a Student's T-test p<0.05. XR+ indicated an absorbance <0.05 units above the blank and a Student's T-test p<0.05. XR weak indicated a response >0.02 units above the negative control with a p-value that was not significant. XR− indicated an absorbance within 0.02 units of the negative control. It should be noted that there can be significant biological variability in the peroxide response due to plant age, location of the disc within the leaf, and other factors. As a result, p-values from the T-test are a guide and not an absolute inclusion criterion.

The results of these studies are summarized in Table 19 below:

TABLE 19 Summary of Peroxide Response Name SEQ ID NO: Soy Tobacco P1-13P-20P 164 ++ − P1-29 130 ND + P1-31 131 + − P3-5 156 ND Weak + P3-9 158 ND ++ P3-10 159 ND ++ P4-14S-9A 57 ++ + P4-14S-9D 58 Weak+ + P4-14S-9S 52 + Weak+ P4-14S-9Y 53 + + P4-14S-12D 59 + + P4-14S-13D 48 ND Weak+ P4-14S-13F 134 + Weak+ P4-14S-13V 133 + + P4-14S-13Q 54 + Weak+ P4-14S-16S 55 − ++ P4-14S-17D 49 ++ ++ P4-14S-20S 56 − ++ P4-14S-21D 50 ++ ++ P4-d10, 14, 18 62 ++ − P4-d18 51 + ++ P4-i10A, 14A, 18A 68 + − P4-i10A 65 ++ ++ P4-i14A 66 ++ ++ P4-i18A 67 ++ ++ P4-116 140 + ++ P4-117 141 ++ + P14 113 + Weak+ P14-22L, 26L 115 Weak+ − P14-22L, 26E 19 ++ Weak+ P14-22A, 26L 20 + + P14-22A, 26E 21 Weak+ − P14-22E, 26L 22 ++ ++ P14-22E, 26E 23 + Weak+ P14-22L, 26A 26 + + P14-22A, 26A 27 ++ − P14-22L, 25-26A 28 ++ − P14-22L, 28-29A 29 Weak+ − P14-22L, 32-33A 30 ++ + P14-22L, 26, 29A 31 ++ − P14-22L, 28, 32A 32 ++ − P14-dc2 122 + ++ P14-dc4 123 ++ ++ P14a 114 ++ ++ P15-60 150 ++ ++ P15-61 151 ++ + P15-62 148 − − P15-63 149 − − P18-8 142 + + P18-9 143 + + P14d-7D 208 ND + P14d-10D 209 ND ++ P14d-11D 210 ND + P14d-14D 211 ND ++ P14d-15D 212 ND ++ P14d-17D 213 ND ++ P14d-18D 214 ND ++ P14d-7S 215 ND ++ P14f-17S 45 ND ++ P6a-15D 199 ND + P6a-11S 204 ND − P15b-12S 188 ND ++ P15b-21S 193 ND ++ P18min-11S 94 ND + P18min-7D 85 ND ++ P19min-10S 107 ND ++ P19min-11S 108 ND + P19min-13S 109 ND ++ P25min-15S 81 ND ++ P25-9D 224 ND + P25-12 153 + + P25-13 154 ND + P25-14 155 ND ++ ND: Not determined

In general, the vast majority of peptides tested XR+ in Soy. However, tobacco was more discriminating. Most peptides that were a single mutation from an HR+ sequence were XR+ in tobacco. Even a second mutation often still resulted in XR+ phenotype. However, tests on p14 variants showed the mutation of three leucine residues to alanine generally resulted in a loss of XR elicitation. Likewise, C-terminal truncated variants of p15 (p15-62 and p15-63) were XR− in tobacco.

Example 3—Root & Shoot Growth Analysis

Peptides were tested for biological effects on the allocation of growth resources to the shoot (above ground) and root (below ground). Peptides were dissolved at 0.2, 2, or 5 μg/ml in a total volume of 100 ml deionized water. Corn or soybean seeds were then soaked for one hour in the peptide solution. Untreated control (UTC) plants were soaked in deionized water. Clear plastic 300 ml beverage cups (Solo®, Dart Container Corporation) were prepared for planting by marking the bottom with a cross, dividing the bottom into four equal quadrants. The cups were then filled with Sunshine Mix #1 soil (SunGro Horticulture) sieved to ¼″. 100 ml of water was added to the soil. Treated seeds were then planted by pressing the seed lightly into the top of the soil. The seeds were then covered with an additional 50 ml of loose soil. Seeds were allowed to germinate and grow for 12-14 days.

The length of the shoot was measured as the distance from the soil to the lightly stretched tip of the highest leaf for each plant. Plants that failed to germinate or exhibited stunted growth were removed from the trial. Stunting was defined as lacking a fully expanded true leaf at time of data collection or having an expanded true leaf judged by eye to be <½ the average leaf area of the treatment group. Generally, 30 seeds were planted per treatment group and 15-25 plants were used for data collection.

Root growth was estimated by counting the number of times that a primary root crosses the quadrant marks on the bottom of the cup. These were often observed along the bottom circumference of the cup, although some were visible along the side of the container and were counted as if crossing a vertical extension of the quadrant line. This number was divided by 4 to produce a root growth index. This index was found to correlate ˜90% with measured total primary root length (sum of lengths of all primary roots after rinsing soil from roots and measuring directly).

The results of these studies are summarized in Table 20 below. Each number indicates the percentage increase over the untreated control values. An asterisk indicates that the difference was statistically significant with p<0.05 as determined by Student's T-test.

TABLE 20 Summary of Root & Shoot Growth Peptide (Host) SEQ ID NO: Rate (ug/ml) Root Shoot P4-14S-9A (corn) 57 0.2 4.8 3.9%* P4-14S-9A (soy) 57 5.0 2.5% 6.5%* P4-14S-9A (soy) 57 2.0 4.3% 5.0%  P4-14S-16S (soy) 55 2.0 28.3%* −11.3%    P4-14S-16S (soy) 55 0.2 28.3%  −2.0%    P4-14S-20S (soy) 56 5.0 2.2% 5.8%* P14 (soy) 113 5.0 24.9%* 4.4%  P14a (soy) 114 5.0 10.3%* −3.5%    P14a (soy) 114 0.2 −2.7%   8.7%*

Increased root growth (shown in p4-14s-16s, p14, and p14a) increases the water-gathering ability of the plant and will increase drought and flooding resistance. Conversely, increased shoot growth (as in p4-14s-9a, p4-14s-20s, and p14a soy at 0.2 μg/ml) increases light-gathering and energy conversion. It is notable that p14a can cause increases in either root or shoot growth depending on dosage. P4-14s-16s causes a strong shift in resource allocation to root growth.

Example 4—Growth Tests

Soy seeds (or corn seeds, as indicated) were planted in flats with 2 seeds per cell within the flat at a greenhouse facility. The seeds were allowed to germinate and the smaller plant is culled, leaving one plant per cell. Once the first true leaves are fully expanded and the second leaves are beginning to expand, the plants were initially measured for height. This was performed by stretching the highest leaf upward and measuring the distance to the soil. Peptides were dissolved in water at the indicated concentrations (Table 21 below). The plants were then treated with a foliar spray using widely available spray bottles until liquid was dripping from the leaves. Six flats of 14 plants each were treated per condition (peptide or control). Designated untreated control plants were sprayed with water. The plants were allowed to grow for 14 days. The height of the plants was again measured and compared to the original height to quantify growth. Finally, the plants were harvested by removing the shoots (all above-ground material). For some experiments, this was weighed upon harvesting to determine the fresh mass (including water weight). The shoots were then dried at 70° C. for 72 hours, and again weighed to determine dry biomass. Although this method uses a similar measure (growth) as in Example 3 above, the treatment method is different (seed soak vs. foliar spray). As a result, the experimental outcomes may diverge.

TABLE 21 Summary of Growth Measurements SEQ Growth ID Rate increase Dry biomass Fresh mass Peptide NO: (ug/ml) (%) increase (%) increase (%) P1-29 (corn) 130 2.0 7.8 5.7 5.1 P4-14S-9A 57 2.0 11.9% 10.8% ND P14 113 2.0 25.8%  1.6% ND P14 113 5.0 31.4%   3% ND P4-14S-12D 59 5.0 −4.2% −3.6% ND; resistant to wilting P14a 114 5.0  8.9% 10.6  83.3% P14a 114 2.0  3.4% 11.0% 57.9% P14a 114 0.2 14.7% 12.6% 46.8% P14-32 124 5.0 12.5%   14% 33.3% P14-32 124 2.0  1.7%  8.2% 27.6% P14-32 124 0.2  9.5%  6.8%  2.9% P14-dc4 123 5.0  −17% −7.6% −15.4%   P14-dc4 123 2.0   −4.6 −1.6%  0.4% P14-dc4 123 0.2  2.6%   5.6%  7.5% ND: Not determined Several of the studied peptides cause increases in growth and dry biomass (p4-14s-9a, p14, p14a, and p14-32). In addition, several peptides caused increased conservation of water as compared with UTC plants which suffered drought stress at trial completion. Conserved water content was indicated by >10% increase in fresh mass, such as found in p14a- and p14-32-treated plants. The growth effect was not limited to soy; corn also exhibited a modest growth benefit upon peptide treatment with p1-29.

Notably, P14-dc4, which incorporates a truncated C-terminus, seems to lose the significant growth, dry biomass, and fresh mass benefits observed for p14. By comparison, removal of the P14 N-terminal sequence (P14a samples) still results in increases for all 3 measures.

Example 5—Induction of Resistance to Tobacco Mosaic Virus

Peptides were tested for the induction of resistance to tobacco mosaic virus (TMV) in tobacco. Briefly, three tobacco plants at 6-8 weeks old were selected per group (samples and controls). The bottom-most leaf of the plant was covered and the plant was sprayed with a solution of water (negative control), peptide, or Proact (positive control). The spray was applied until the leaves were fully wetted, indicated by liquid dripping from the leaves. The plants were then allowed to dry and the leaf covering was removed.

Three days post-treatment, the previously-covered leaf and a leaf on the opposite side of the plant were then lightly dusted with diatomaceous earth and 20 ul of a 1.7 ug/ml solution of purified tobacco mosaic virus was applied. The TMV solution was then spread across the leaf surface by lightly rubbing solution and the diatomaceous earth across the surface of the leaves. Two minutes after inoculation, the diatomaceous earth was rinsed off the leaves with water. 3 days after TMV inoculation, the leaves were scored based on the number of TMV lesions observed. The leaf was also scored for signs of the hypersensitive response, including yellowing and wilting of the affected leaves.

Effectiveness described in Table 22 refers to the % decline in TMV lesions on treated vs UTC plants. A reduction of TMV on covered leaves indicates a systemic immune response in the plant while reduction on uncovered leaves indicates a local response. Asterisks indicate that the P-value derived from a T-test was <0.05.

TABLE 22 Summary of TMV Resistance SEQ Effectiveness Effectiveness ID Concentration Uncovered Covered Peptide NO: (ug/ml) (%) (%) P1-29 130 10 44  18  P1-31 131 20 95* 88* P3-5 156 10 66  94* P3-10 159 20 94* 95* P4-14S-9A 57 5.0 84* 86* P4-14S-9D 58 10 89  52  P4-14S-12D 59 5.0 61* 60* P4-14S-13Q 54 10 40  61* P4-14S-16A 60 10 1 3 P4-14S-16S 55 10 72* 46  P4-14S-16V 135 10.0 78  85* P4-14S-17F 136 10 94  57  P4-14S-20S 56 10 59* −45    P4-14S-20V 137 10 −26    −29    P4-14S-21D 50 10 49  48  P4-111 132 10 58  65  P4-115 139 20 87* 87* P4-116 140 10 52   0* P4-d18 51 10 65  15  P4-d10, 14, 18 62 10 55  37  P4-i10a 65 10 92  81  P4-i14a 66 10 75  77  P4-i18a 67 10 81  50  P4-i10, 14, 18a 68 10 75  69  P14-22L, 26L 115 20 65* 67* P14-22L, 26E 19 20 70* 91* P14-22A, 26L 20 20 48  62  P14-22A, 26E 21 20 91* 85* P14-22E, 26L 22 20 61* 84* P14-22E, 26E 23 20 74* 62  P14-22E, 26A 25 20 89* 88* P14-22L, 26A 26 20 72* 83* P14-22L, 25-26A 28 10 87* 75* P14-22L, 28-29A 29 10 83* 84* P14-22L, 32-33A 30 10 91* 69* P14-22, 26A 27 10 92* 93* P14-22L, 26, 29A 31 10 85* 70* P14-22L, 28, 32A 32 10 71* 37* P14-31 129 20 85* 87* P14-32 124 20 90* 82* P14-dc1 121 10 65* 46  P14-dc2 122 10 76* 56  P14-dc4 123 10 34  19  P14-39 160 20 72* 66* P14-41 245 20 86* 61* P14d-7D 208 20 71* 55* P14d-10D 209 20 84* 84* P14d-11D 210 20 81* 87* P14d-14D 211 20 84* 35  P14d-15D 212 20 87* 74* P14d-17D 213 20 68* 65* P14d-18D 214 20 52  32  P14d-7S 215 20 −112    23  P14f-17S 45 20 94* 84* P6a-15D 199 20 74* 74* P6a-11S 204 20 71* 88* P15b-12S 188 20 76* 47  P15b-21S 193 20 100*  97* P18min-11S 94 20 −90    −274    P18min-7D 85 20 26  29  P19min-10S 107 20 81* 94* P19min-11S 108 20 71* 45  P19min-13S 109 20 35  −70    P25min-15S 81 20 81* 74* P25-9D 224 20 78* 55  P15-60 150 20 55  13  P15-61 151 20 55* 7 P15-62 148 20 94* −122    P15-63 149 20 90* 74* P18-8 142 20 55  78* P18-9 143 20 65* 52  P25-9 152 20 68  87* P25-12 153 20 77* 58  P25-14 155 20 52  −87   

Several HR-negative peptides cause significant local and systemic responses: P4-14S-9A, P4-14S-17A, P4-14S-12D, and P4-14S-16V produced the best results. In general, most peptides exhibited some anti-TMV activity. However, peptides with a larger C-terminal truncation as compared with an intact HR-box (see co-pending U.S. patent application Ser. No. 14/872,298, entitled “Hypersensitive Response Elicitor Peptides and Use Thereof”, filed Oct. 1, 2015, which is hereby incorporated by reference in its entirety) (e.g., p4-116, P14-dc4), exhibit reduced effectiveness against TMV infection. A shorter C-terminal truncation generally elicited TMV resistance at a slightly weaker rate (50-75% control). Greater disruption of residue spacing in P4-d10,14,18 also exhibited a moderate reduction in effectiveness against TMV infection. Also, mutation of some leucine positions seemed associated with weaker TMV responses: P19 min-135, P18 min-7D, P18 min-11S, P14d-18D, P4-14S-20V, P4-14S-20S, P4-14s-16A. Notably, although it contains a several hydrophobic sequences, P25-14 exhibits weaker control of TMV infection. A systematic investigation of mutation of the important leucine and isoleucine residues over several HR-eliciting sequences revealed that mutations at the several locations can cause a reduction in the immune response. Mutation of the first hydrophobic residue (in p14d-7S, p18 min-7D, and p25-9D) can cause reduced efficacy on covered leaves, indicating a reduction in systemic immune response. P15b-12S also exhibits a similar reduction in systemic responses in the covered leaf. P19 min-13S exhibits poor immune activation. One can remove the last hydrophobic doublet, which still allowed for anti-TMV activity (for example in P1-31 and P1-111). However, a further shortened hydrophobic sequence is associated with a reduction in activity against TMV, as demonstrated by P4-116 and P14-dc4.

Having thus described the basic concept of the invention, it will be rather apparent to those skilled in the art that the foregoing detailed disclosure is intended to be presented by way of example only, and is not limiting. Various alterations, improvements, and modifications will occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested hereby, and are within the spirit and scope of the invention. Additionally, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations therefore, is not intended to limit the claimed processes to any order except as may be specified in the claims. Accordingly, the invention is limited only by the following claims and equivalents thereto. 

What is claimed:
 1. An isolated peptide comprising the amino acid sequence of L-X-X-(L/I)-(L/I)-X-X-(L/I/V)-(L/I/V)  (SEQ ID NO: 116), wherein the peptide is free of cysteine and methionine; each X at positions 2, 3, 6, 7 is independently selected from the group consisting of G, A, S, T, D, isoD, E, γ-glutamate, Q, N, K, and R; the peptide comprises up to 24 amino acids at the N-terminal end of SEQ ID NO: 116, up to 10 amino acids at the C-terminal end of SEQ ID NO: 116, or both, except that the amino acid sequence of the peptide does not comprise (L/I/V/F)-X-X-(L/I/V/F)-(L/I)-X-X-(L/I/V)-(L/I)-X-X-(L/I/V/F)-(L/I/V/F) (SEQ ID NO: 125) where each X at positions 2, 3, 6, 7, 10, 11 is any amino acid; the peptide has a Kyte Doolittle hydropathy index of less than 0.3; and the peptide induces an active plant response, but does not induce a hypersensitive response, when applied to mechanically disrupted plant tissue.
 2. The isolated peptide according to claim 1, wherein the peptide comprises up to 20 amino acids at the N-terminal end of SEQ ID NO: 116, up to 7 amino acids at the C-terminal end of SEQ ID NO: 116, or both.
 3. The isolated peptide according to claim 1, wherein the amino acid sequence of the peptide contains no lysine or arginine residues except optionally at the C-terminal end.
 4. The isolated peptide according to claim 1, wherein each X at positions 2, 3, 6, 7 of SEQ ID NO: 116 is independently selected from the group consisting of G, A, S, T, D, isoD, E, γ-glutamate, Q, and N, and wherein the peptide further comprises an arginine residue at the C-terminal end of the peptide.
 5. The isolated peptide according to claim 1, wherein the isolated peptide is characterized by one or more of: (i) stable when dissolved in water or aqueous solution, (ii) resistant to chemical degradation when dissolved in an aqueous buffer solution containing a biocide, (iii) solubility of greater than about 0.1% in water or aqueous solution.
 6. The isolated peptide according to claim 1, wherein the active plant response induced by the peptide is selected from the group consisting of peroxide induction, enhanced growth, pathogen resistance, biotic or abiotic stress resistance, and modified biochemical signaling.
 7. The isolated peptide according to claim 1, wherein the peptide is at least 90% pure.
 8. The isolated peptide according to claim 1, wherein the peptide is a fusion polypeptide comprising a second amino acid sequence coupled via peptide bond to the amino acid sequence.
 9. The isolated peptide according to claim 8, wherein the second amino acid sequence includes a purification tag.
 10. The isolated peptide according to claim 9, wherein the second amino acid sequence further includes a cleavable linker sequence between the purification tag and the amino acid sequence.
 11. The isolated peptide according to claim 8, wherein the peptide is a fusion polypeptide comprising a first amino acid sequence for said peptide linked to a second amino acid sequence for said peptide.
 12. A fusion polypeptide comprising a plurality of amino acid sequences linked together in series, one of the plurality of amino acid sequences comprising a peptide according to claim
 1. 13. A composition comprising one or more peptides according to claim 1 and a carrier.
 14. The composition according to claim 13, wherein the composition is a clarified cell extract.
 15. The composition according to claim 13 further comprising an additive selected from the group consisting of fertilizer, herbicide, insecticide, fungicide, nematicide, a bactericidal agent, a biological inoculant, a plant regulator, and mixtures thereof.
 16. The composition according to claim 15, wherein the additive comprises either: (i) clothianidin, a combination of clothianidin and Bacillus firmus, imidicloprid, or a combination of imidicloprid and Bacillus firmus; or (ii) thiamethoxam; a combination of thiamethoxam, mefenoxam, and fludioxynil; a combination of thiamethoxam, mefenoxam, fludioxynil and azoxystrobin; a combination of thiamethoxam and abamectin; a combination of thiamethoxam, abamectin, and a Pasteuria nematicide; or a combination of thiamethoxam, mefenoxam, fludioxynil, azoxystrobin, thiabendazole, and abamectin; or (iii) a biological inoculant comprising a Bradyrhizobium spp., a Bacillus spp., or a combination of a Bradyrhizobium spp. and a Bacillus spp.
 17. The composition according to claim 13, wherein the carrier is an aqueous carrier.
 18. The composition according to claim 17, wherein the aqueous carrier further comprises one or more of a biocidal agent, a protease inhibitor, a non-ionic surfactant, or a combination thereof.
 19. The composition according to claim 13, wherein the carrier is a solid carrier in particulate form.
 20. The composition according to claim 19, wherein the solid carrier is a dry powder.
 21. A method of imparting disease resistance to plants comprising: applying an effective amount of an isolated peptide according claim 1 to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to impart disease resistance.
 22. A method of enhancing plant growth comprising: applying an effective amount of an isolated peptide according to claim 1 to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to enhance plant growth.
 23. A method of increasing a plant's tolerance and resistance to biotic stress comprising: applying an effective amount of an isolated peptide according to claim 1 to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to increase the plant's tolerance and resistance to biotic stress factors selected from the group consisting of insects, arachnids, nematodes, weeds, and combinations thereof.
 24. A method of increasing a plant's tolerance to abiotic stress comprising: applying an effective amount of an isolated peptide according to claim 1 to a plant or plant seed or the locus where the plant is growing or is expected to grow, wherein said applying is effective to increase the plant's tolerance to abiotic stress factors selected from the group consisting of salt stress, water stress, ozone stress, heavy metal stress, cold stress, heat stress, nutritional stress, and combinations thereof. 